In racing, we have in certain circles what is known as Balance of Performance. It is actually called that, but in many other forms of racing it’s not called anything, but it has the same intent. That is, regulation of the innovation in order to provide a level playing field. And it is applied sometimes on a team-by-team basis.

When you really think about that concept, it really doesn’t make sense. Rules are one thing, and I and many others are of the agreement that we need rules, to a point. When rules are enacted for the sole purpose of holding back a more innovative and hard-working team, or teams, then the concept has gotten out of hand.

The way this whole thing called auto racing got its start was that there were very limited rules and a lot of imagination and hard work. If a team began to dominate, the other teams didn’t cry and complain, they just respected the winning teams and then tried to work harder to beat them.

Is having a dominant team good for the sport, some might ask? When the Green Bay Packers were dominating pro football back in the early 1960’s, it caused the other teams to buckle down and work harder and smarter. Then eventually other teams grew in strength to overcome the dominance of Green Bay. And it grew pro football because of it.

But what if the league in their infinite wisdom told Green Bay that since they were winning so much that they had to change quarterbacks (i.e. carburetors), or add fifty pounds to each player to kind of slow them down. And what if the league didn’t want the fans to know what they were doing lest there be a revolt.

That is exactly what is happening in auto racing in a lot of areas. It is happening in circle track racing as well and it needs to stop. It is ruining the sport that was born and bred on innovation and hard work. And it’s all because of a few less innovative teams who cannot beat the winners. It’s also because of promoters who don’t want the dominant team to “stink up” the show.

Then there is the sponsorship angle. What if the sponsor for the track or series were to also sponsor one of the teams racing there. The sponsor likes to see their car win, but another team is always winning instead. They go to the track or series management and want something done about this situation. “They must be cheating” the sponsor says.

So, the hard working team all of a sudden gets extra treatment in the tech shed and lo and behold, some little technical infraction that had nothing to do with the performance, suddenly gets discovered and they end up getting disqualified. This happens in even the most visible of series. I’ve personally witnessed it in action.

Then you have honest series and forms of auto racing. A couple come to mind, like dirt racing where there are few rules. If you make weight after the race and your body panels pass inspection before the race, you can keep your win.

Formula One has a lot of rules, but the construction and engine rules allow complete innovation within certain overall parameters. If a team dominates for a year or more, then the other teams must play catchup. And F1 is very popular globally. That formula has not diminished the sport, it has actually grown it.

Way too many promoters, series and tech officials feel that they have to control their racing. No, you don’t. You need to set rules for everyone and then let things play out. If a certain team, or teams, end up winning most of the races, then so be it.

When winning teams are singled out just for winning and made to follow a different set of rules, that to me is sacrilege. It goes against everything racing is about. And, it will kill the sport. Everywhere we see over-regulation that produces cookie-cutter cars, or “pack” racing is doomed to failure.

Everywhere we see the allowance of innovation and fewer rules, we see growth. Dirt racing is growing and has been for some time, as is F1. Those two should be a model for the industry on how to conduct your racing program.

Editor’s Note: We had asked readers to tell us about how their track was being managed related to safety and these are some of the responses we got. As promised, where appropriate, no readers names will appear.

Track Safety Comments

Hello Bob,

I read your article about track safety from May 2017, and wanted to let you know about a local dirt track in Calhan Colorado. The track name is El Paso County Raceway in Calhan, Colorado. It is County owned but not operated by the County.

When anyone questions the promoter on how to get in touch with someone at County when we have and continue to have issues, he becomes very belligerent, verbally abusive, curses yells at people and makes such a scene trying to scare others to not ask questions. Let me list some of the issues that have and continue to happen:
– County personnel state that the promoter is given $20,000 per year for track maintenance. This track is the worst track in Colorado with ruts, dirt and rocks chunks of concrete that have damaged cars and so much dust from early on every race day fans complain about the dust, drivers and photographers complained to no avail.
– There’s usually accidents that cause an individual or individuals to have to be transported to medical facility and the promoter hurries the races to begin again with no medical personnel nor ambulance available and if questioned about it he disappears into his large toy hauler and ignoring safety concerns again.
– He doesn’t have trained staff that can handle safety properly, he has several young ladies working race nights and others that are a mix of people that will kiss his b.
– He will start a pit meeting off each race night immediately cursing at and or about people, Facebook issues, yelling and threatening people and claiming “SAFETY” first but then his own kids drive through the pits on golf carts or four wheelers way too fast. Then one particular night we had a rain delay and he gets on PA system yelling at people to get their cars on the track we’re going to get these main events ran!
– When there are accidents, the flag man is not quick enough to notice and is late putting out the yellow which has created more accidents.
– Local photographers have had to jumped in many times to help during accidents because there is no track safety personnel.

Thanks, Name Withheld

It would seem, from a liability standpoint, the county would want to know what is going on. I’m sure you can find out who would be interested. Our point in doing these kinds of exercises is to educate the promoters. If they can see what is being done in other parts of the country in a more responsible way, then they might alter their approach.

Track Safety Comments II

Mr. Bolles,

I submit the example of what a fire / safety crew should be: Lawrenceburg Speedway. Their team is what every track should have.  In other words, a 10. As a photographer that has shot F1, Nascar, IndyCar, MotoGP, etc. for 25 years at Indianapolis Motor Speedway I have seen the best there is in action in the Holmatro Safety Crew.

I can honestly say the Lawrenceburg crew is the short track equivalent. Their gear and techniques are well above any other short track in the midwest and the dedication to the drivers and teams is amazing.

Thanks, Andy Clark.

Track Safety Comments III

Bob,

I am responding to your request to rate the tracks safety crew performance.  We are very fortunate at Nodak Speedway in Minot ND to have one of the most dedicated safety crews around. The head of our safety crew has been doing this since he drove a brand new Vega station wagon, which he volunteered for additional safety vehicle.

We are also very fortunate to have a sponsor whose son was in a wreck involving a fire.  Anything we want, we get.  Our sponsor built our current rescue vehicle and equipped it with jaws of life, and auxiliary hydraulic unit.  We also have the local Fire Extinguisher shop as a sponsor, so gear, chemical, hoses are very easy to come up with.  We have an Air Force Base close by, so many of our volunteers come from there. Our rescue truck has 4 people assigned at all times plus we have a side-by-side that was donated to use for quick response / fast attack.

The real problem Bob, as I see it in many tracks, is getting qualified volunteers.  Nodak host extrication training every year where they bring in old cars and cut them up plus drivers bring in their cars so they can practice removing drivers from the car.

Our problem lately has been getting EMT/Paramedics.  We have 1-3 dedicated people, but things come up and sometimes they are left shorthanded. This year Nodak Speedway has gone back to having an ambulance with trained personnel on hand at a cost of $500 per night. Due to Nodak Speedway’s level of training and personal who are willing to help, I will rate them a 10 out 10.

Jeff Barta

Nodak is one of the good ones, obviously.

Anti-Squat Question

Hello Bob,

I am reading and article in Circle Track from February, 2017 on the anti-squat. I was wondering if you move both trailing arm up to the top hole for more forward bite off the corner or just one side and if it’s one side which side do you recommend.

Thank you, Mike

What I was saying was that by shortening the leverage arm, you can produce more force on the third link. We can do that by moving the third link down, and/or moving the trailing arms up. You should do both trailing arms.

Remember not to change your trailing arm angles when doing this. Don’t just move the rear mounts up or you will be changing the arm angles quite a bit and those angles regulate the amount of rear steer, not to mention rear alignment.

Gentlemen’s Agreement Comment

Hello

I read your story about the gentleman’s agreement and calling your own mistakes if you spin somebody and thought I would offer my view of it. I run a dirt Wissota B mod in northern WI. Our yellow flag rules are if you spin a car or pinch a car down into the inside or the wall and cause them to stop you are tagged with the yellow and go to the back and the other driver gets their spot back.

Also, if you spin but save it and another car spins to avoid hitting you then you are also caused with the yellow and go to the back. Yes, there are a lot of judgment calls but also several times where the wrong call was made and the offending driver stopped and told an official it was his fault, it got sorted out.

You are correct in saying that many drivers have the “I do nothing wrong ever, its always the other driver.” Some have the mind set of “well if they weren’t on the track they wouldn’t have been hit” who think they own the whole track and do slides for life as we call them. They start on bottom of the corner and slide all the way to the top coming out and don’t car if you are there or not.

As far as myself, I have always gone to other drivers and admitted if I made a mistake and hit them going in or messed up a corner and caused a wreck. Sometimes it goes bad and other times I get a look of confusion which sometimes later turns to a thank you or respect later. Racing dirt we lean on each other time to time and never say anything about it.

I had a incident last year where I rear ended a driver on a restart due to I caught the green flag better than he did and pushed him into the infield. I lifted and let him get sorted out and come back on track and gave him his spot back and we kept racing. Never threw a yellow. After the race he was still in his car and I told him I was the one who hit him and why and apologized. His response was ” I didn’t think it was on purpose since you only did it once.” After the race he came and said thank you for apologizing and said if I need anything just ask.

Another thing is if drivers would go and be calm and talk rather than storm over and yell and swear at each other there would be a lot less issues. That also goes with officials. Any of the tracks I run at I have a great relationship with the officials because I talk to them rather than yell and scream. A simple “Can I talk to you for a minute? ” or ” Will you explain why this call was made?” without any sarcasm in the tone goes long, long way. That’s just my take. Thanks for taking the time to read this.

Cy Hoaglan

Well said, I’ve got nothing to add.

If you have comments or questions about this or anything racing related, send them to my email address: chassisrd@aol.com or mail can be sent to Circle Track, Senior Tech Editor, 1733 Alton Parkway, Suite 100, Irvine, CA.

The post How to Regulate Short Track Racing to Death appeared first on Hot Rod Network.

In the Truth piece in this issue we learned that certain control arm angles in a double A-arm suspension will create the ideal tire contact patch for a particular race car. We discovered through testing and evaluation that a larger contact patch provides more traction in a tire, much like increasing the loading, but not needing to.

Having that knowledge is very important, but not knowing how to apply that knowledge would be sad. So, continuing along on that thread, let’s dig deep into the issue of cambers and camber change so that we might apply this fresh knowledge to our own car. Let’s figure out what we need to do in order to have the best tire contact patch.

Camber Change Basics

I’m going to run through this quickly because we have covered this so many times that shame on you if you haven’t learned this yet. Camber change mostly happens because the chassis and control arms move.

Most double A-arm suspensions are of the short arm/long arm design. That means that the upper control arm is shorter than the lower control arm. As such, when the wheel moves vertically, the arms move on a different radius and the upper ball joint moves more laterally than the lower ball joint. This creates a change in the camber angle.

There are two motions that will change the camber in a wheel/tire. One is vertical motion of the chassis. The other is chassis roll. In almost every form of racing, except with bumps setups, there is some combination of those two motions when transitioning into the turns.

We must consider both of those motions when planning out our control arm angles. With chassis vertical motion, in dive, both wheels move towards negative camber. In an upward motion, both wheel move towards more positive camber.

In chassis roll (roll to the right in a left turn), it is a little different. On the right side, chassis roll moves the RF wheel towards less negative camber while on the left, chassis roll moves the LF wheel towards less positive camber.

So, summing up here, on the right side, in a left turn, chassis dive and roll create opposite motions. They can be made to cancel each other out to attain zero camber change. More on that later.

On the left side, in a left turn, chassis dive and roll both move the wheel towards a less positive camber angle. This motion and the amount of camber change can be mitigated, or reduced as we are about to learn.

How Cars Are Constructed

What you will have to deal with, and the amount of work you will have to undertake is directly related to how your car is constructed in the first place. A car with plenty of adjustment for arm angles and one where it is legal to do so will be much easier to dial in as to camber change and maximizing contact patch area.

First on the list of difficult cars are the stock classes where the rules limit how much you can do and in what areas you can work. Whatever you can do to these cars to get them closer to ideal will make a huge difference in performance.

Then we have the dedicated race car chassis that was built wrong to begin with. Earlier model Modifieds, some of which still exist and are racing, were built so that the upper arm angles are all wrong for proper camber change design. Proper camber change is defined as being near zero change, or as close as you can get to that. We’ll delve into that particular design in a minute.

Road racing cars, even the most expensive types in some cases, lack proper camber change design and I have personally made changes to a few of those cars that made a remarkable difference in how they turned transforming an understeer car into an oversteer car with one quick adjustment.

One More Thing

Before we get started into the nuts and bolts of this thing, there is one more peripheral thing to understand about cambers. Each brand, and each different construction of the tire within the same brand will require a different camber in order to achieve the largest contact patch area.

This is important because if you have a dominant car where you’ve figured all of this out and then go to a track where they run Goodyear tires instead of your usual Hoosiers, you’ll quickly find that you are out to lunch due to needing different cambers.

Sidewall stiffness and the tire cord construction differences will require different cambers and some tires will just flat out create a bigger contact patch than other types. You may never get the car to turn as well with a new brand of tire as it did with your old brand. That you will have to live with.

Starting With a Blank Sheet

To make this easy to explain, let’s start with a blank sheet of paper. We can imagine we are designing a race car chassis and its geometry from scratch. We know what we have evolved into with most dedicated race cars using, from the Truth article, either the moment center theory or the jacking force theory. But how did we get there?

Our first example is a car with level upper control arms. I am going to use a simple geometry software program to find the results of camber change and report those findings to you so you can see how this goes.

We have a late model dedicated fabricated offset chassis with fairly normal conventional dimensions. The left upper arm is 10.5” long, the right upper is 9.0” in length. The right side static camber is negative 3.0 degrees and the left side static camber is positive 4.0 degrees. The left lower control arm length and angle is 15.5” and 2.5 degrees and the right lower control arm length and angles are 17.0” and 1.0 degrees. We will maintain these settings throughout the test and only make changes to the upper control arm angles.

For comparison, we measured the moment center and it is -1.3” height and -14.5” left of centerline before we dive and roll the chassis.

Zero Degrees Upper Arm Angles

With zero degrees of upper arm angles we dive the chassis 1.0 inch and roll it 3.0 degrees. If you are running conventional setups without bumps or coil bind, these numbers are very representative.

Using the above starting cambers, after the dive and roll, we end up with a left dynamic camber of positive 0.9 deg. and a right dynamic camber of negative 0.5 deg. We lost 3.1 deg. of left camber and 2.5 deg. of right camber.

The left dynamic camber is less than we really need for that tire. On the right front, we probably need a full three degrees or more of negative dynamic camber for that tire to work, so if we add the 2.5 degrees of lost camber angle to the static 3.0 degrees, we would then need to start with a negative 5.5 degrees of negative static camber. Does this sound familiar?

And by the way, we still have a moment center location of -2.0” height and -14.0” width (negative is left of centerline), which is close to what we had at static ride height.

More Upper Arm Angle

Now let’s put 15.0 degrees of angle in each upper control arm. To clarify, we are referring to an angle with the chassis mount lower than the ball joint in this case. We will adjust the lateral spacing on the chassis mount to maintain our 4.0 deg. of positive static camber on left side and the negative 3.0 deg. of camber on the right side.

Now after the 1.0” of dive and the 3.0 deg. of roll, we end up with positive 1.4 degrees of left side camber and negative 3.4 degrees of right side camber. The right side actually gained some negative camber instead of losing it.

The left side camber lost much less camber and the 1.4 degrees would work much better. Less loss and a camber more in tune with what the tire wants is a good thing. But can we do better.

Fine Tuning the Camber Change

Our right side camber is much better, but if we wanted zero change in camber, we might fine tune the upper angle so that the camber stayed the same after dive and roll. So, we change that right upper arm angle to 13.5 degrees. After dive and roll we end up with the same 3.0 degrees of right camber we started with. We have achieved the desired zero camber change for the right front tire.

At the left side, let’s add upper arm angle to say 25.0 degrees. When we do that, after dive and roll, the dynamic camber is now 1.7 degrees. We now lost only 2.3 deg. verses the 2.6 deg. when the upper angle was only 15.0 degrees.

Going a little farther, let’s say we put in 35.0 degrees of left upper control arm angle and see what happens. That means that the chassis mount is now a full 6.0 inches lower than the ball joint. After dive and roll, we end up with a dynamic camber of positive 2.0 degrees and only lost 2.0 degrees of camber. Less camber change is better, but there are structural limits to how much angle we can put into a control arm. But you get the point.

For design purposed, for this car, we can probably be satisfied with upper control arm angles of 25 to 30 degrees on the left and 13 to 15 degrees on the right. Remember that this is a sample car and what you run for a setup and the track you will be racing at will generate different dive and roll numbers. These numbers might not work well for your car.

Cambers for Bump Setups

When we look at the cambers for bump and coil bind setups, we still agree that there will be very little chassis movement when the car is on the bumps, but from the time the car leaves pit road until it enters the turns, there will be plenty of camber change going on.

We can live with this huge amount of camber change because it occurs on a part of the track where there is little, or no, lateral force and the cambers and contact patch size doesn’t really matter.

But let’s look at what camber change does take place. With our sample car, we will enter the dive and roll numbers we could typically see for a bump setup. The dive for a car with a 4.0” static ride height and a 0.5” safety factor would be 3.5” of dive. The roll for most of those cars is at or under 1.0 degrees, so we’ll use 1.0 deg.

Putting in those numbers with a left upper angle of 30 deg. and a right upper angle of 13.5 deg. gives us a dynamic left tire camber of negative 5.8 deg. and a dynamic right tire camber of negative 8.2 deg. This is horrible for the LF tire, we need some amount of positive camber, not negative. And we have excessive negative camber for the RF tire.

What we need to do is change the upper arm angles to reduce the camber change from the high amount of dive and adjust the static cambers. Let’s start with the upper control arm angles. If we go back to say 20 degrees on the left upper and 5.0 degrees on the right upper, we’ll see less camber change.

After that change, we see dynamic cambers of negative 2.5 deg. on the left and negative 5.3 deg. on the right. This is much better, but we now need to change the static cambers. If we need a positive 1.5 degrees for the left tire dynamically, then we need to add that number to the dynamic negative camber of 2.5 deg. for a total of 4.0 deg. additional static camber. Adding 4.0 to the current static camber of 4.0 deg. gives us 8.0 deg. of static camber needed to yield 1.5 deg. of dynamic camber after dive and roll.

On the right side, we can take away some of the negative camber. We are gaining 2.3 degrees on the right side after bump dive and roll, so if we reduce the static camber by that amount, we’ll end up with 0.7 deg. of static RF camber.

From all of this we have learned that the upper control arm angles dictate how much the cambers will change for a particular setup. The static settings for control arm angles and cambers will be much different for conventional setups with low amounts of chassis dive and higher chassis roll than we would use for bump setups with high amounts of vertical chassis travel and low amounts of roll angle.

What Does the Tire Need?

Early on we talked about what the tire needs for camber. We are talking about the front tires obviously because there is little we can do to adjust the rear tire cambers for a straight axle suspension. Each brand of tire has different sidewall stiffness and tire construction for the tread support and so need different cambers so that we can end up with the largest contact patch possible.

Like we also pointed out, you may be able to extract a larger contact patch from one tire brand than any other tire of the same tread width and sidewall height. Tire temperatures can point us in the right direction, but we are finding that the driver may be the best litmus test.

As for tire temperatures, a softer sidewall tire can be cambered so that the tire surface temperatures on the side closest to the inside of the turn are 20-25 degrees hotter than the surface temperatures on the outside away from the turn. This difference is achieved with higher camber settings which tend to cause the inside of the tire to flatten out.

Lower tire pressures help us accomplish the goal of producing a larger tire contact patch, but we are not advocating low tire pressures that compromise safety. We do know the trend in racing is to run as low a tire pressure as we can get away with and this is an indicator of the importance of increasing the contact patch area.

Conclusion

All of this works to point us in the direction of maximizing the tire contact patch area for our race tires. If we can understand how cambers change, what causes that and how we can minimize the change, we can work to get more traction in our race cars.

The post Creating Better Traction Through Camber Changes appeared first on Hot Rod Network.

When I learned that my friend needed help setting up his dirt hobby stock car, I jumped at the opportunity. This little project allowed me to apply some of the technology we provide in CT to a car with limited adjustment capability.  Once we got into the car, I was surprised by our discoveries. What we do to this car can also be done to a Street Stock or similar type of car.

The problem with this car that was had built late last season was that it would not turn well and as a result would push on entry and go loose on exit. There are probably a few thousand or more teams in this country that have the same problem. So, I saw an opportunity to jump in there, do an evaluation to try to fix it.

The car is a 1985 Monte Carlo and has the metric four-link rear suspension, a stock frame throughout and must use stock type springs in their original positions. The shocks are mounted in the stock positions and the car has retained all stock suspension parts.

As with most “stock” classes, teams are allowed to trade stock pieces from other model year cars as long as the brand is the same. This class also runs large Hoosier racing tires all around where-as the street stock classes are only allowed one racing tire on the RF.

Breakdown – The first order of business was to weigh the car on the scales and measure and record the ride heights and the spindle heights for future reference. We wanted to maintain the original ride heights after installing new springs so the geometry would be the same and we needed to know the spindle height so we could check for proper clearance and make sure there was no bind of the ball joints while the car was on jack stands.

We then proceeded to break the car down and remove the springs and shocks to see what we had.  To get the front springs out, we had to remove the upper ball joints. This gave us a chance to inspect everything up close. My helper, Kenny Hellyer, was very familiar with the mechanics of these cars and was a definite asset in all of our re-design work.

The first problem we noticed was that the shocks on both sides in the front were rubbing on the inside of the height adjuster that was put into the car not to jack weight, but to create the ride height that was necessary to avoid bottoming out. The rear of the car had legal spring height/weight jacking, adjusting bolts.

The shock contact was so bad that one shock was leaking and both housings were bent severely. These were aftermarket twin tube shocks and still seemed to be working. I tried the standard method of checking them by placing one end on the floor and pushing in from the top. The shocks were so stiff that they barely moved.

I don’t know if someone chose really stiff compression numbers or if the shocks might have been bent, but these units were not helping the situation. On dirt, we must have shocks that will allow the car to run over the holes and bumps and move fairly easily. They must control the springs, but not be so stiff as to cause the tire to skip or bounce.

Front Geometry – I inspected the front geometry and noticed that the car builder had used the taller Impala spindles which reduced the lower control arm angles. He also had lowered the upper control arm mounts to gain more upper control arm angle. Both of these changes are highly recommended for this class. Using taller spindles actually improves both upper and lower arm angles.

The geometry I saw looked a lot like previous cars I have fooled with in the stock classes and I knew the moment center was close to where it needed to be, at or very near the centerline of the car. Had this work not been done, we could have expected the MC to be somewhere outside the car making the front end overly stiff.

The cambers were not what I would have expected or chosen. The LF was a little less than one degree and the RF was around 5 degrees. This is typical of a car that transfers a lot of load to the RF as that tire is forced to carry most of the front load and work hard to turn the car. The LF doesn’t need camber because it isn’t working very hard anyway. We needed to make camber changes to reflect how the front end would work after the redesign.

We reset the cambers to a positive (+) 2.0 on the LF and minus (-) 3.5 at the RF. Once we re-spring the car to allow a more balanced setup, the LF tire will definitely be working harder and take some of the load off of the RF tire. So, we would end up needing more LF camber and less RF camber. Our tire contact patch will be optimal with these changes.

Inspection of the caster settings revealed that the RF caster was in the negative range (upper ball joint forward of the lower ball joint) and the left side was positive. That would cause the steering to want to turn right, maybe good for sliding the car through the turns, but we were going to make this car turn well, so I opted for a different plan.

We moved the right upper ball joint back to create about two degrees of positive caster and that matched the left side caster. This way, the steering would be neutral and the driver could steer both directions without feeling a difference in resistance.

We were a little worried about possible binding of the ball joints with the increased upper control arm angles. So we cycled the spindles beyond what they would see on the track and found we had plenty of clearance. Always check to see if there is any binding or tightness in your suspension while you have the springs and shocks off the car.

Spring Rates – We next checked out the spring rates that were installed in the car. The fronts were marked as: LF = 1100 lb./in. and the RF was 1200 lb./in.  The front springs had a half round of the coil cut off, so the actual rate, although we did not measure them, was obviously higher than they were marked.

The rears springs were: LR = 225 and the RR = 150.  The rear had too much spring split, even for a Metric 4-link rear suspension with a high roll center. With the front spring rates being so high, this combination in the rear caused a lot of load to transfer to the RF on entry and through the middle of the turns overloading that tire. That would definitely help cause a push.

After careful consideration, we installed the following springs: LF = 900, RF = 850, LR = 225, and RR = 175.  The front reverse spring split with the softer RF spring helps corner entry and promotes front roll angle while the reduced spring split in the rear facilitates the high Metric moment center to help control the rear roll while not going too far.

Here is a further explanation of this.  For a balanced setup, we need for each end of the car to desire to roll to about the same angle in the turns. We have discussed this concept many times in Circle Track. A high rear moment center reduces the desire to roll, so if we don’t soften the RR spring, the rear will be stiff and not allow proper compliance.

That would overwork the RR tire and cause a loose off, if not totally loose, condition. Running a RR spring that is too soft compared to the LR spring would have the opposite effect. The rear would want to roll over more so than the front and the car would be tight, or tight/loose off. There is an optimum spring split, RR softer, that will keep the car close to a balanced dynamic state and help the car on entry, through the middle and provide more bite off the corners.

Shock Installation – Because the front shocks were hitting the spring height adjuster, we needed to make a correction. We noticed that the stock hole where the top of the shock was anchored was positioned at the factory well towards the outside edge of the spring on both sides of the car.  With stock shocks and springs, this would work for clearance, but with our setup and equipment it was not.

The fix was to create a new “stock” hole farther inward and closer to the center of the spring. We reinforced this new hole by welding a washer on top of the frame. This provided a good bit of spacing between the spring spacer and the shock body.

To make sure we were good with the rules against using front weight jackers, we welded the height adjuster so it would not turn. This made it a spacer rather than a weight jacking device. We also installed a new set of gas pressure “stock” replacement shocks that were made for racing and more like what should be used on this type of car.

Tire Pressures and Sizes – I reviewed the existing tire sizes versus the tire pressures they had been running. The sizes were LF = 83.75, RF = 83.75, LR = 84.5 and RR = 85.0.  This only allowed a half inch of stagger in the rear, not nearly enough for this track. This too would facilitate a tight car.

The cold tire pressures they had been running were: LF = 17psi, RF = 23psi, LR = 15psi and RR = 14psi. The RF was high and the RR was low on pressures.  The fix was to try to change the tires around while re-pressuring the tires so that we could get front and rear stagger.

I traded the RF tire and the LR tires. This put a larger tire at the RF and a smaller tire on the LR.  We re-pressured the tires to: LF = 18psi, LR = 16psi, RF = 22psi and RR = 16psi.  With those pressures, we now had a front stagger of 1.00 inch and a rear stagger of 1.50 inches.

Weight Distribution – When we weighed the car before making any changes, the cross weight was at 53%.  After installing the new springs, changing the front caster and camber, moving tires around and adjusting tire pressures, we re-set the cross weight at 48.5%, or about 75 pounds of left rear weight.

With only 48.2% rear weight, the car did not need the 53% cross which represented 216 pounds of left rear weight. This was yet another reason why this car was way too tight. It was cross weight tight and was driving off the left rear tire under acceleration.

Another thing I noticed and corrected was the placement of lead in the rear of the car. The car builder had placed a considerable amount of lead well behind the rear end, on the rear hoop that protects the fuel cell. Although fairly common, this tends to create a cantilever effect and increases the polar moment. Polar moment is defined as a force trying to rotate or swing the rear end to the outside wall during cornering.

Some teams will experience a more neutral car by placing lead well behind the rear end, but this is more like a crutch for a tight car and although it helps the car into and through the turn, it will make the car loose off. It is much better to set up the car correctly and get the front to turn with a balanced spring setup and proper moment center and cambers. That way, you get into and through the turns better and still have more bite off.

It is always a good practice to keep all lead mounted inside the axles. We may decide later on to move it out, but for now we remounted the lead in front of the rear end and high in the car. A higher center of gravity is desirable on dirt cars for dry and slick tracks.

The Results – Once we got the springs installed, the tires mounted, the cambers set, the air pressures set and the ride heights and weight distributed like we wanted, we stood back and took a look at the car. It just looked better right away. I’ve seen lots of hobby stocks and this one looked like it was ready for the track.

The first chance we got to run the car, the driver noted that this car was now even better than his original Hobby Stock. The difference was that it turned better which allowed him to maneuver past guys that were hanging it out trying to point the car to get off the corners. And it had much more forward bite than before due to the more straight ahead attitude.

With his smooth and relentless style, this car was just what he wanted. If you prefer to sling the car in sideways, fight to get control and then hope for some semblance of bite off, then you might not want to copy us. Good luck and good racing.

Sources:

Afco Racing
www.afcoracing.com
800-632-2320

Allstar Performance
www.allstarperformance.com
269-463-8000

AR Bodies
www.arbodies.com
615-643-8827

Capital Motorsports Warehouse
www.cmwraceparts.com
800-278-2692

Five Star Bodies
www.fivestarbodies.com
262-877-2171

Harbor Freight
www.harborfreight.com
800-423-2567

Moser Engineering
www.moserengineering.com
260-726-6689

Optima Batteries
www.optimabatteries.com

QA1
www.qa1.net
800-721-7761

Quick Performance
www.quickperformance.com
515-232-0126

The post Fine Tuning the Stock Division appeared first on Hot Rod Network.

The third link can refer to either the upper link in a traditional three link rear suspension, or it could refer to a lift arm, pull bar, or torque arm. Those too make up a third attachment that restricts rear end rotation from the torque forces of engine acceleration.

When you change the angle of the third link, or possibly the spring rate of a pull-bar or lift arm, there are certain things you need to pay attention to. Also, there are reasons to make changes to the links we mentioned and we will discuss those too.

Drive Shaft -Pinion Angle – The driveshaft to pinion angle is one of those critical settings we have talked about in the past. If you have made sure your angles are correct, and we sure hope you have, then when you make changes to the third link assembly, whatever that may be, we need to think about how the change might affect our driveline angles.

If you move a traditional third link front mount down to increase the angle, you will be rotation the rear end and the driveline angles will change, not only at the pinion, but at the transmission also. That is if the mount is vertical and not radiused. And the change won’t be the same at each end. So, we end up with a miss-aligned driveline.

If we install a different spring in a pull-bar, or lift/torque arm, it will compress more or less depending on whether you installed a softer or stiffer spring. What you should have done in the original installation is take into consideration the compression of the spring and where the rear end will be positioned under full throttle acceleration. That is where we need the driveline angle to be correct, not when it is at rest.

There is an easy way to bring back your driveline angles. If the link were solid, then just check the rear end angle before the change and reset it after the change by adjusting the length of the third link. That was easy.

If you have a link with a spring, then you need to figure out how much differently the link moves with the new spring. We can do that with a small amount of math. If our spring compressed 2.0 inches with a 600 ppi (pounds per inch) rate and we install an 800 ppi spring, it will move less with the stiffer spring.

To find out how much less, we do a simple division. If, say, the 600 ppi spring compressed 2.0 inches, then the new stiffer spring will compress 600 ÷ 800 x 2.0-inch = 1.5-inch, and that equals the new travel. Just subtract the new travel from the old travel (2.0-inch – 1.5-inch = 0.5-inch) to get how much you need to move the end of the link at the spring to adjust the link angle.

Force Adjustment – To adjust the force magnitude the link will produce, we make a different adjustment than changing the springs. Changing the spring won’t alter the force of anti-squat, just the speed and amount of movement of the link.

To adjust the force, we need to do one of these things: 1) change the angle in a traditional solid, or sprung, three link, 2) change the height off the rear end (keeping the same angle) of the traditional solid or sprung three link, 3) change the length of the lift or torque arm from the center of the axle to the front mount.

An increase in traditional third link angle will create more anti-squat force. A shorter distance from the traditional third link rear mount to the axle will increase the anti-squat force too. A shorter distance from the axle to the front mount on a lift or torque arm will increase the anti-squat force.

Force Placement – We can adjust the placement of the force created by our third link, whatever the design, by moving it left or right in relation to the rear tires. These links put not only a lifting force on the chassis, but also a downward force on the rear end and ultimately the tires that replaces some of the load on the rear ride springs.

Since we are taking load off the springs and onto the tires through the rear end, the placement left and right dictates how much of the displaced load goes onto each rear tire. If the link is placed midway between the two rear tires, then 50% of the loading goes onto the left tire and 50% goes onto the right tire.

If the link were closer to the left rear tire, say 40% of the rear track width, then 60% of the displaced load would go onto the LR tire. If we had a magic calculator that would tell us how much load ended up on each rear tire, and the LR was 10% less than the RR tire, we could move the third link 10% closer to the LR tire and cause a more equally loaded rear tire scenario for greater traction.

To cause this redistribution of load, we have to physically move the third link position. That’s not easy to do in some cases. And, we don’t want to move it too far either. If the LR needed 10%, more loading and we move the link 20% closer to the LR tire, we are back where we started with unequally loaded tires, only in reverse of where we were to begin with.

To give you some kind of idea how far we are talking about, 10% of a track width of 65 inches is 6.5 inches. So, based on that, if you want to make a 10% change in the force distribution, you would move your third link 3.25 inches towards the LR tire if that is where you need more force.

Conclusion – As with the other changes we talk about in this issue, we need to think out what we are changing that isn’t in our original thoughts. Step back and take a good look at what you are doing and try to imagine what else is going to be affected by your changes.

And as always, try to do only one change at a time. Either change the angle of your third link, or move it laterally, not both at the same time. Or, change the spring rate or the length of the lift/torque arm, not both.

The post Third Link Suspension: Why and How To Make Changes appeared first on Hot Rod Network.

Changing camber in your front wheels is pretty straight forward, right? There are some things that are inadvertently altered when we change our cambers. Let’s go through the process and see that we might need to consider the overall effect of making camber changes.

Why Change? – The reasons why we might want to change cambers include the following. We might see where the tire temperatures are not ideal in our view for the type of car, type of tire and design of race track we are running at. We also might want to experiment with camber to see if the tire could use more and provide us with more traction. The tire temperatures might look good to us, but hey, what the heck, let’s see if more is better.

Tire temperatures are not really the final determining factor in judging whether we have the best camber in our front tires. In some suspension designs, the tire can roll through camber changes such that temperatures rise across the tread, but the tire is never at the ideal camber. The temperatures lie to us sometimes. I’ve personally seen this happen.

An example of this is the NE pavement Modifieds, being the SK division as well as the Tour Modifieds. Some teams run very little right upper control arm angle, close to 5 degrees or so. With that angle, the tire runs the straightaways on the inside edge, the transition on entry on the middle of the tire and the mid-turn on the outside. When the team checks the tire temperatures, they might look OK. But the tire never has the best tire contact patch.

You can get a clue this is happening by simply observing the car going through mid-turn. I once visited with the late and great Teddy Christopher and went with him to Stafford for an SK race several years ago. I watched him in practice through turns one and two and noticed that the RF tire was going into positive camber.

Back at the pits he asked me what I thought. I said it looked pretty bad, not really in those words. I talked to his crew chief, a seasoned veteran, and we found out where he had gone wrong. He had been fooled as well. When he made changes to the control arm angles on the car that next week, Teddy went out and won two or three in a row, not that it was unusual for him to do that. But the team had been struggling as of late and that change helped them a lot.

The moral of the story is, when your car goes out, look at the tires and see if they look like they have the camber you think they need on the race track. Visuals can tell us a lot.

Basic camber knowledge tells us that on a circle track, turning left, we need positive camber in the left front tire and negative camber in the right front tire. When the chassis travels in dive and roll, these cambers will change. How much depends on the control arm angles, especially the upper angles.

Ride Height – When we decide we need to change the cambers, we need to know what else we are changing when we do that. A quick camber change on pit road does not just represent the “one change at a time” edict like we, and others, have preached for years.

On the left front, the spindle inclination, or angle of the ball joints from a front view, is usually less than at the right front. I’m used to 5-7 degrees of angle. This puts a lot of the tire outside the intersecting line that passes through the ball joint centers.

As such, when we add positive camber to the left front, we essentially jack up the chassis. In other words, we load the LF and RR more so which unloads the RF and LR corners. This de-wedges the car (reduces cross weight for you new guys) and can make the car looser.

If the car turned better after the change, we might think that the added camber did the trick when in reality it was the drop in cross weight that made the car turn better by making it looser.

At the RF corner, if we take away negative camber, we add to the wedge, or cross weight, of the car. Since that spindle has a higher degree of inclination, the intersecting point falls closer to the tires center of contact patch. So, the effect is less than at the LF.

If the LF addition of positive camber de-wedges the car and taking away of negative camber at the RF adds to the wedge in the car, then they might cancel each other out, right? No, because for each degree of change in camber, the LF changes the wedge more than the RF does. The net is still a looser car, but how much is dependent on the amount of camber change and the overall design of the suspension.

If we add positive camber to the LF and also add negative camber to the RF, we have really loosened up the car because both of those actions took wedge out of the car. Boy, she’s turning now, Jack. But not necessarily because the camber change caused the tires to work harder.

The bottom line here is this, when you change the camber in one wheel, bring the ride height back to normal, or what it was before the change. Then you wouldn’t have changed the cross weight percent and loading on the four tires. At least not statically.

Bump Setup Camber Change – With the advent of the bump setups in circle track racing, camber change of any significant amount while on the bumps is a thing of the past. But we’re not out of the woods yet. There is still a lot of camber change going on from when the car is on the grid to when it is going through the turns.

So what, we might say. The tires are loving it because our cambers are staying very close to ideal due to very little vertical chassis movement. And you’d be right, but what about the transition onto the bumps? What happens during that process? Few teams consider what happens then. Let’s see.

As we have discussed above for a more conventional car, when we change the cambers, we are also changing the corner heights and along with that, the distribution of loading on the four tires. If the chassis travels some three or three and a half inches down onto the bumps, where does the wedge, or cross weight, go to then? It has to change, we have already discussed that little tidbit.

Weight change due to the jacking effect of camber change (and that is essentially what it is, the tire jacks up, or down depending on the change) also changes the loading on the four tires.

We already know that the extreme travel associated with bump setups, from ride height to on-track height will most times load the sway bar. This adds cross weight to the setup. If the camber change from all of that travel changes the cross weight too, then where do we end up? Good question.

Finding Loaded Cross Weight – The major point made here in this piece is that camber change will change the loading on the tires and we have to know this in order to plan for it in our preparation of the race car.

If we know how much the cross weight will change due to chassis travel, then we can adjust our cross weight percent with the car at ride height. Say we gain 2% of cross weight at full travel, then all we need to do is set 2% less cross weight in the car at normal ride height.

Put the car on the bumps only with the bar loaded and see what the cross weight goes to. Then adjust your cross weight percent with the car at ride height. It’s as simple as that.

Or, you can adjust the bump spacing to the shock body to bring the cross weight percent back to what you want while on the bumps. That will compensate for the sway bar and the camber change that happens due to the high amount of travel.

The post A Few Secrets to Making Camber Changes appeared first on Hot Rod Network.

We have often talked of the need for brake bias adjusting. We need for the bias adjuster to be centered when we have the correct amount of braking force in the front verses the rear. There are several ways to do that.

We will not only tell you the different ways to go about that, we’ll now tell you how much your bias is expected to change with each different part. That’s important because if you don’t know the degree of change, you might just end up with the wrong parts, again.

Of course we are talking about a car with a bias adjuster in the pedal assembly. And we are assuming you can change the master cylinders easily. For this discussion, we are also going to assume that making changes to the calipers is more difficult and expensive. So, let’s just leave those alone for now.

We are discussing making changes to the master cylinders and showing you how much each change in size means in overall braking bias change. The percent of change in braking force each size of master cylinder causes could also be applied to the cylinder sizes of the calipers if you so choose to go that route.

Why Change The Brake Bias? – We will need to change the system for bias change if the brake pedal bias adjuster is off center. We might have the bias we need in the system, but it’s never a good idea to have a bias adjuster off center.

An adjuster that is centered is much more consistent and provides the same braking power lap after lap, whereas one that is off center might be a little different each time you apply the brakes. Consistency is important in all of your race car systems.

If you have used up all of your pedal bias adjuster adjustment and are still not where you want to be on brake system bias, then you’ll definitely need to make changes to the master cylinder sizes and the change will be more than if the adjuster were centered to get the adjuster back to center.

Sizes Of Master Cylinders – The most common sizes of master cylinders and their associated areas of bore are: 5/8-, ¾-, 13/16-, 7/8-, 15/16-, 1.0-, and 1 1/8-inch. As we will see, the percent of change from one size to another is most on the ends, from 5/8- to ¾-inch and from 1.0- to 1 1/8-inch.
Another important factor to consider when choosing master cylinder sizes is the amount of brake fluid flow each produces. The smaller the master cylinder, the more the brake pedal will move to move the calipers the same amount.

It takes X amount of fluid to push the brake pads onto the rotors. If the master cylinder was larger, it would move a greater amount of brake fluid per inch of brake pedal movement. So, the pedal will move less with a larger master cylinder. That may be good, or not so good depending on your application.

Master Cylinder Bias Vs. Caliper Bias – Another important thing to note is that we have two bias’s going on with our brake system in most cases. We have master cylinder bias which we are discussing today, and then we have brake caliper bias, which we might, or might not make changes to.

It is sometimes easier to change a brake master cylinder, or two, than change the calipers. For one, the master cylinders are less expensive, so if you need a size you don’t already have, your cost is less by changing the master cylinder size to achieve a bias change.

If we end up with a master cylinder bias of 50/50, we are still going to have a caliper bias with the front having more braking power than the rear because the front caliper is always larger than the rear caliper.

So, as you think out your bias changes, take into account the difference in caliper sizes, the adjuster position, and what the master cylinder sizes are. Always go larger in size to make changes, no matter which way you go so that your pedal travel will not increase to create a mushy pedal.

That means, if you need more rear braking, you go up on the front master cylinder size, not down on the rear cylinder. And if you want more front braking bias, you go up on the rear master cylinder size, not down on the front. Both of these changes produce less pedal travel, not more.

Sources:

AFCO Racing
www.afcoracing.com
800-632-2320

Hawk Brakes
www.hawkperformance.com
330-722-4295

Performance Friction Brakes – PFC Brakes
www.performancefriction.com
800-521-8874

Wilwood Motorsports
www.wilwood.com
805-388-1188

The post How to Adjust Brake Bias appeared first on Hot Rod Network.

I wrote a column several years ago discussing why we do what we do here at Circle Track. I think it is important to re-address that topic and I was recently motivated to do that by a “reader” who wrote to me explaining what he liked in a racing magazine and what he did not.

He is, or was, a long-time racer and his likes now are coverage and nostalgia type of articles that can frankly be found in numerous other good and solid publications. But, it’s not what we do here at CT. And I don’t begin for a minute to apologize for our lack of feature articles about racers present and past.

What we do, and do very well, is provide this industry and its participants, with cutting edge technology and content that runs anywhere from race car design and setups, to engine building and tuning, to driver and race track safety and beyond. If it’s technical and related to racing, we do it.

We made the decision to go this way back in the early 2000’s because that is what the racing community both needed and wanted. At that time, and even today, there are plenty of places to get coverage, but few places to get real present day technical information that the reader can use to win races.

Our advertisers appreciate our approach too. They are in the business of designing, manufacturing, and/or selling parts and information that helps the race teams go faster and win more races, period. The goals of CT and our advertising partners are the same.

I used to read CT back in the late 1980’s and through the 1990’s and attended the early CT Trade Show and Expo in Daytona Beach where I’d drool over the many race parts and cars that were displayed there. I’m not sure if we were the first trade show, probably not, but we did advance the concept by seizing the opportunity to reach racers who came to this town during February for the annual races during Speed Weeks.

Then the CT show faded and PRI, Performance Racing Industry trade show, started into business. Early on it was located in Columbus, OH and I attended those shows too. Now we are about to attend the 2017 version of PRI, a continuation of what the CT trade show was years ago.

The home of PRI is now in Indianapolis, IN, a location that is much more central to the racing community than was the CT trade show in Daytona, or the PRI show held some years ago in Orlando, FL. It brings together like minds that are constantly searching for that next new thing that will bring excitement and performance to their racing program. It’s like a bunch of kids in a candy store watching all of the attendees move about the floor. And CT will be there with full participation.

We will continue to influence the industry in a positive way and you, the racer helps us to do that. We don’t build the race cars and parts, or even come up with many of the ideas we present, we just recognized a good thing when we see it.

Many racers have experimented with using springs as bumps long before our articles and subsequent testing, or the move to smaller sway bars instead of the big ones in the early BBSS setups. We just recognized a good thing. What we do is keep our finger on the pulse of the industry, look for new and better technology, and then offer it up to the masses. You guys get it most of the time, and that makes us happy.

What is the next new thing? Come to PRI and find out. It will be there, trust me. This show has grown so large, it threatens to outgrow the convention center again, like it did about ten years ago when it had to be moved to Orlando. But that is a good thing and speaks well of the growth of the sport and industry.

At any rate, I have been a part of CT for over fifteen years now and it is the job of the contributors and Editor Matt to make sure the tradition continues. And when you get your new copy of CT, or when you go to Facebook or the CT website, you will see cutting edge technology and content that will drive the industry forward whether it’s our ideas or yours.

After all, it’s not important who comes up with a great idea, it is important that we share those ideas in order to move our sport forward. Thanks for taking an interest in CT and allowing us to participate in your racing program. We all get smarter as a result.

If you have comments or questions about this or anything racing related, send them to my email address: chassisrd@aol.com or mail can be sent to Circle Track, Senior Tech Editor, 1733 Alton Parkway, Suite 100, Irvine, CA.

Toledo ARCA Incident

(Editor’s Note: This reader did not want this published, but the information is too good, and I could not do it justice in any other way than to just present it, so we will hold back the name and any reference to whom shared this with us.)

Bob,

Even though I am about now removed from my involvement with ARCA, when I was there, training was never an issue with the safety crew. Their Safety Initiative was ahead of a lot of racing series that would surprise you.

ARCA required a neck collar for the driver long before any other stock car racing organization. This was in the days before the HANS or Hutchens Device. It turns out it wasn’t the best option, but they were looking for answers before anyone else. They were the first to require gloves, which was risking the organization itself in the way lawyers can twist things around.

ARCA was one of the first to have a full-time traveling safety co-coordinator, which let the drivers know who was there and who was in charge of the safety crew, no matter who they were, or at what track they were at. All safety officials who were under the employ of ARCA attended safety classes at Toledo Speedway then later at UNOH.

I’m not sure why ARCA has not made a statement following an investigation, unless I missed it, but my belief would be that someone turned cars loose on the track before checking around the track, by radio, that ALL safety personnel were in position and ready beforehand.

One miss-understood circumstance was where the truck was parked. Smoke wasn’t an issue then, but as more and more smoke developed, the wind was blowing in a direction that happened to blow the smoke toward the truck, which WAS parked properly, in a way to protect the accident scene, and with the front end pointed in the direction they wanted any approaching car to go.

One thing I have noticed at Toledo Speedway when the ARCA Racing Series is there, there is an overlap of perceived “bosses” and crews. You have the ARCA Series officials, who do things one way, and the Toledo people who have their procedures, and chain of command. Remembering both groups are ARCA employees, the Indians now have too many Chiefs. I believe that’s where the problem REALLY lays. My guess is somebody was taking orders from a “boss” who was not informed that the other’s safety crew wasn’t in position.

I’m sorry to run on but I am personally sick to my stomach every time someone keeps citing lack of training in this case. Training is far from the issue unless hiring idiots became the standard after I left. Then we had the right people doing those jobs, plus the ability to do those jobs, with everyone else’s full confidence. Now making it come across as no one had any skills is a disservice to ARCA, their teammates, and a cheap shot at the dedication of those involved with the safety of the series.

Anyway, I have a saying, “It’s not what it is, it’s what it looks like”. In this case, those involved “looked” liked amateurs. But, most likely it was what you “didn’t” see or hear that was more a contributing factor.

There is always another side to the story. I am sure whatever went wrong on that day will be corrected and the lives and safety of the participants will be improved. I thank this reader for providing valuable information regarding the series and history of safety of that series.

Track Safety Comments

Bob,

I wonder what goes through some promoter’s minds. I came up with a plan to line the corners at Lee Speedway in NH with the foam blocks like the ones at Oswego Speedway and Lancaster Speedway. Simply use them as advertising billboards and have the advertisers pay for the blocks.

Lee would have none of it because it wasn’t their idea. They gave some excuse about cleanup. So, let’s clean up dead drivers instead. They even ran an Ironman class backwards. Some drivers pulled off, seeing the danger in doing so, like hitting a wall ending head on. They even brag that if you hit their concrete wall that you’re gonna get hurt. I don’t think that promoters put the driver’s safety high on their list.

Bill Stergios, Candia, NH

Thanks for your comments, Bill. I don’t know the situation with Lee Speedway at all. But it is up to the drivers to decide what is safe and what is not. Your comment about the drivers pulling off because of safety issues is what needs to happen at any race track if the conditions are not as good as they need to be.

Foam, in defense of Lee Speedway, is very hard to clean up and the very small foam pebbles spread across the track would only make the situation worse for those who have to race after someone has hit the foam and spread those tiny pieces across the track.

But, there are other solutions that could make a track safer and we hope all race tracks take a look at their facilities and try to imaging what could go wrong, then fix it. That’s all it takes, just think. In many situations, we can look in hindsight and see where the problem was. Let’s look ahead for a change.

BBSS Setups?

Mr. Bolles,

Thank you for the great articles. I follow you monthly and apply as much as I can. I have a couple of questions. You mentioned in the November issues that the BBSS set ups are a thing of the past and most have moved to bumps with a smaller bar. I race at a 1/2 asphalt track in the mid-west and run a limited late model rules package (Big Eight Series) that does not allow bumps or binds.

We are not allowed to have anything that limits the suspension travel.  What would you recommend? We are running the BBSS set up traveling the front suspension about 5″.
I use a Performance Trends software program to determine my moment center. Statically, it sits at 4.7” off the ground and 3.6” to the left.

Knowing that a majority of the front end travel comes in corner entry braking and factoring in the tie down shocks that hold it down, I use 3.5 inches of dive and 2.5 degrees of roll to analyze dynamic moment center. This moves it to 1.0 inch off the ground and 10.3 inches to the left. Am I correct in my dive and roll numbers?

Again, in the November issue, you reference 1 inch of dive and 2.5 to 3 inches of roll. With my big bar (675#) it doesn’t seem like the car rolls that much. I have attempted to remove as much camber gain as I can but with the dive and roll used above I still gain about 5 degrees in the right front.

My temperature numbers are consistent at about 20-25 degrees hotter on the inside and the RF and RR average are within 10 degrees of each other depending on how the car is handling, tight or loose. On my program, any changes I make to reduce gain, takes the moment center out of bounds. Should I continue to work to reduce this? If so can you give me some ideas? RF upper sits at about 12 degrees static, left upper is 19.5 deg. and the lowers are flat.

Do you have any experience with a Track Star ll rear end? I have installed one and am struggling with it. Car is tight. Any help would be appreciated.

Thanks for your time, Brian G.

Brian,

Your bar must be a medium or heavy 1 3/8″ bar? That is not what is considered a big bar, just on the large normal side. Big bars are 1.5″ to 2.0″ diameter. It is too stiff as far as what we are seeing used today.

The 2.5 deg. of roll is probably too much, but if you can go out and not brake hard for a few laps and then look at your shock travel, you’ll get a good idea of the roll angle.

Yes, you will have a lot of camber gain on the RF with the amount you are traveling. As to the moment center, the lowers should have angle and be staggered, usually we see 2.5 deg. on the left lower and 1.5 deg. on the right lower. These can vary, but that stagger works well most of the time to control the lateral movement of the MC.

With the Track Star and similar rear differentials, you cannot run much stagger, like 1/2″ or so or they will not work from what I understand. You need to talk to the manufacturer about that.

The post Why We Do What We Do at Circle Track appeared first on Hot Rod Network.

It sounds pretty simple, just change a spring, right? There are some things to know before you change a spring in a race car. Some of these are simple and a no brainer, while others are not that obvious or difficult to understand, but necessary in order to do the spring change correctly.

Ride Height – This first tip is known by almost every racer on the planet, but if you are new to the sport, here you go. When you change a spring, and that usually means you are changing the spring rate with a new stiffer or softer rated spring. You will then need to adjust the spring height so that the ride height remains unchanged.

There is a saying in racing that holds true most of the time. It is, don’t make more than one change at a time. That way, whatever happens to the cars handling can be attributed to that change. If you change more than one thing, you are left guessing which one, or if both, caused the change in handling.

At ride height, we have a load distribution on the four tires. We measure these loads with a set of scales, or at least I hope you do. We want those loads to remain unchanged after we change a spring. So, you need to measure your ride height, coil-over length, etc. so that you can adjust the spring height to bring the ride height back to what it was before the spring change. Then the tire loads will remain unchanged.

If you change the spring angle, such as in a dirt Late Model or Modified, in order to change the rate the car will feel and the spring base, you will have also changed the ride height and load distribution if you don’t adjust the height of the spring.

Putting more angle in the coil-over will lower that corner of the car, so you’ll need to raise the spring height to compensate. Putting less angle in the coil-over will raise that corner of the car and you’ll need to back off on the adjuster ring a bit to get the ride height back to normal.

Only change one spring at a time. If you don’t, things will get confusing really quick. After you change the spring, roll the car back and forth before you check the ride height measurements again to settle the tires.

Shock Change – When you change your spring rate, you will need a different rate of shock to control that spring. If you are making a significant change in spring rate, the shock change will also need to be significant.

Basically, a stiffer spring will require a stiffer rebound rate to control the stiffer rebound reaction of the spring. The shock can also be changed to have less compression because a stiffer spring resists compression more so than a softer spring.

An example would be going from a conventional setup to a bump setup. In these setups, the right rear spring you will need will be stiffer than what you ran for the conventional setups. Therefore, you’ll need a shock that is stiffer in rebound rate.

Balance Change –  When you change your spring rates, you are not only changing the travel of that corner, you are changing the handling in a lot of cases, especially in the rear.

Say you need more heat in the left front tire, so you surmise that a stiffer RR spring rate would force more loading on that tire. This is the way many racer think, and they would be right, but for reasons they probably didn’t consider.

A stiffer RR spring, when the other springs have not changed, will alter the dynamic balance of the car. The rear will roll less and since it is attached to the front end by way of a stiff chassis, it will roll less too. This change will cause those two to now by out of balance, if they were in balance before the change.

This imbalance in this case does cause more load to end up on the LF tire at mid-turn, but at the expense of the dynamic balance, which we value a lot to make the car more consistent.

If you change the RR spring, or the LR for that matter, you’ll need to make a change to the panhard bar (rear moment center height) so that the dynamic balance stays the same. If you increase the RR spring rate, you’ll need to lower the panhard bar. If you increase the LR spring rate, you’ll need to raise the panhard bar.

Panhard Bar Change – If you change the RR spring rate, then the amount of travel that spring will experience through the turns will also change. A stiffer spring will travel less, all other things being equal to before the spring change.

If it travels less, the right end of the panhard bar (assuming the car has a right side chassis mount for the panhard bar) will then end up being higher that it was with the softer spring. If you can determine how much less the new spring travels than  the original spring, you can then adjust your panhard bar height down so that it will end up at the same height as when the softer spring was in the car.

You can check the shock travels to find out how much different a new spring travels than the old spring. Use this difference as a measure of how much to change the panhard bar height. If there is a motion ratio between the end of the panhard bar and the spring, then allow for that ratio when changing the bar height.

Rear Steer – Many chassis are built such that they can rear steer when the chassis rolls. Most teams will adjust the trailing arm angles to eliminate the rear steer. If you change a spring, that can cause rear steer due to the change in spring movement.

If you have determined the ideal right side trailing link angle, and then change how much the RR corner of the car travels, then you must change the trailing arm angle so that your rear steer amount will remain unchanged.

A RR that travels less (from a stiffer installed spring rate) will need less trailing arm angle than before the change to a stiffer spring rate. That is because it will end up at a different height after the chassis rolls.

The RR corner of the chassis will be higher with the stiffer spring rate, so if you don’t change the height of the front of the trailing link, it will end up higher than before the change and that will steer the rear end differently.

Conclusion – In any change you make to your chassis, consider what other parameters might also change as a result. Think about how the chassis will move differently and then make sure you compensate for that difference. Your setup and handling will stay much more consistent if you do.

Sources:

DRP Performance Products
www.drpperformance.com
888-399-6074

Gale Force Suspension
www.galeforcesuspension.com
251-583-9748

Intercomp Racing
www.intercompracing.com
800-328-3336

Longacre Racing Products
www.longacreracing.com
800-423-3110

The post Methods Used to Make Spring Changes appeared first on Hot Rod Network.

The reasons why and the methods we use to change the rear trailing arm links are many.  Those lie somewhere in among the various ways we try to improve our performance. But there are ways to do this and ways not to do it. And, we need to be aware of other settings we might be changing when we make changes to the trailing arm angles.

Rear Square – Of primary importance in our overall setup routine is making sure we know which way the rear end is pointed. By pointed, we mean, where is a line that is at ninety degrees off of the axles pointed. This is also the direction of the wheels and tires. In most cases, we want them pointed straight ahead at normal ride height.

We can check this by employing a simple routine using strings and marks on the floor. Or, we can use lasers in todays advanced setup tool environment. Either way, we want to make sure we know where the rear is pointed.

Which Way To Point On Asphalt– The next step is determining which way we want the rear end to point in the three basic phases of the turns: 1) Entry, being the initial turn-in during braking, 2) Mid-turn, meaning the part where there is no deceleration and no acceleration called steady state because all of the motions are steady now, and 3) the Acceleration phase where we need the most bite off the corners we can get.

On the entry phase, it would be nice if the car turned in easy so we can brake more straight ahead, at least having the front wheel more straight ahead. If the rear turned the car during that initial phase, we won’t need to steer nearly as much. But this phase doesn’t last long and we don’t want the rear to steer very long at all or we will go loose as we enter the middle phase.

As we enter and travel through the middle phase, we want the rear to be steered straight ahead, or even slightly to the left which will provide the tires with more angle of attack and therefore, more grip.

We have to be careful here because if we give the rear tires too much grip, the front won’t be able to turn with the rear and we’ll be tight through the middle phase. A little rear steer goes a long way.

Then as we begin to accelerate, we need maybe more rear steer to the left to give the tires even more angle of attack and counter the torque of the motor making the rear tires slip. This “slip” angle can be produced by causing more rear steer. In any case, we’ll need for the rear to either be steered straight ahead coming off the corners, or steered slightly to the left.

We can position our trailing links so that as the car enters the turns and rolls to the right, the right trailing arm pushes the right rear tire back, steering the car into the turn. Then as the car rolls more to its final roll angle, the right trailing arm travels past level to now going downhill and pulling the right rear tire back to where it was originally. The trailing arm angle we talk about here is when the front mount higher than the rear axle mount.

Now the RR tire and the rear end is pointed straight ahead and ready for the mid-turn phase. We can even set the RR trailing arm angle so that it travels a little more and then pulls the RR tire forward a slight amount to give the rear tires more angle of attack and more grip.

But what about the left rear link? This link does not usually move much during initial entry, and even through the mid-turn phase on most low and medium banked tracks. It’s only when we drive through very high banked tracks that we see any significant LR chassis travel to affect the LR trailing arm angle.

What we do see is LR travel when the car accelerates off the corners. It is here where we can make a difference and produce rear steer, to the left. If we put angle (front mount higher than the rear axle mount) in the LR trailing link, then as the car squats coming off the corner, it will move towards level and then push the LR tire back causing rear steer to the left, like we need. We can vary the amount of steer by varying the angle of the link.

Which Way To Point On Dirt – Dirt control arm angles are a bit more complicated. Depending on the system, you can create many different scenarios for dirt cars. The most common systems are the three-link, four-link and Z-link. We’ll concentrate on the four and Z-link systems because the three link is talked about in the asphalt section.

Both the four-link and the Z-link systems have four links. The four-link has them all going forward from the axle, whereas the Z-link has the bottom links going forward and the top links going back from the axle.

These two systems can be setup to do either of three things, 1) produce zero rear steer, or not move the wheel/tire either forward or back, 2) produce forward movement of the tire, or 3) produce rear movement of the tire. In most cases, its only one of those per wheel.

And, we need to think about which way the chassis moves, up or down. With some link angles, we get jacking forces in the left rear links that push the left side of the chassis up on acceleration. It is almost inevitable that the LR tire will be pulled forward when this happens. The amount of travel forward is dependent on the link angles.

The right rear chassis might move down, up or stay at the same height as the car enters, goes through mid-turn, and then accelerates off the corner. No matter what the movement is, we can keep the RR tire in the same position fore and aft if we set the right link angles and do all of the steering with the left link angles.

There are various thoughts and opinions on why we steer the dirt cars so much through the turns. It may look like the car is loose and the rear tires are sliding, but they are not. They are just pointed to the right and must travel out way past the path of the front tires in order to gain their angle of attack to get around the corner.

The most popular thought, and one that is most true practically, is that having this extreme rear steer gets the car turned in better and pointed to come off the corner. But mostly it provides a flat plate aero effect that puts the large flat side of the car at an angle to the direction of travel causing a side force that helps to counter the lateral force trying to push the car off the turns. And on dirt, especially dry slick dirt, we need all the help we can get.

How To Make Changes – We need to make sure when we change our link angles that we don’t inadvertently change the rear alignment too. If we take a measurement from the wheel rim forward to a point on the side of the car, we can then recheck that distance after the change to bring the tire back to its original position fore and aft.

Some cars have alignment tabs that can be used too, but make sure your alignment tabs are correct before you rely on them. And if you have a laser system, you can easily check the rear alignment after a link angle change. Remember, make only one change at a time.

The post How to Change Trailing Arm Angles Properly appeared first on Hot Rod Network.

Back in the heyday of Cup racing, I attended track tests put on by some of the top teams at various tracks, and one of the things many of them did was make changes to the upper control arms. At that time, I didn’t quite understand why they would do this. Maybe they didn’t, either.

I think this may still be happening today, although I don’t think anyone has figured out why it does what it does. The truth is, some of those changes made the car turn better. If a team found the right control arm angle and length, and the car went faster, then the experimentation worked.

In the way we understand control arm angles today, it’s all about camber change and moment center location. When a team does make a change, hopefully they know what result they are looking for and what control arm angle will give them that result. Let’s take a look at some issues with making changes to control arm angles.

Length Affects Angle – Left Side – If you change your left upper control arm length from 10 to 11 inches, you have changed the angle if you bolted it back into the same holes in the upper chassis mounts.

For example, we have a front end with a 28 degree angle in the left upper control arm and it is 10 inches long. If we change that arm to an 11-inch arm and don’t change the mount height, the angle changes to 25.3 degrees. We would need to lower the chassis mount half an inch to get the 28 degree angle back.

If our original thinking was that a longer control arm would reduce the camber change in the left wheel, then we would be wrong, because the camber change actually stayed the same due to the change in control arm angle. Longer was better and less angle was worse. They canceled out.

Length Affects Angle Right Side – OK, so upper control arm length doesn’t really affect camber change on the left side, but what about the right side? Let’s experiment on that side and see what happens. We have an 8.5-inch right upper arm with a 12 degree angle and after dive and roll, our camber goes from (-) 3.5 degrees to (-) 3.9 degrees. We are gaining 0.4 degree of camber.

Going to a 9.5-inch upper and bolting it into the same height holes in the upper chassis mount, we end up with (-) 3.4 degrees, a loss of 0.1 degree, while the upper angle changes to 10.7 degrees. And if we maintain the same original angle of 12 degrees, our camber goes to 3.7 degrees, still a gain of 0.2 degrees of camber.

The change in length only created a moderate difference in camber change, but the angle made a greater difference in camber change: 0.2 degrees with length only and 0.5 degrees with angle and length change.

Going back to the beginning statements, it looks as though the early crew chief changes to the arm length only, and bolting the arm back into the same holes did make a significant difference in right front camber change and the handling would have also changed.

Angle Affects Camber? – In fact, on this car, which represents a typical front end layout in today’s late-model asphalt race car, the length doesn’t make much change at all on either side. The angle is what influences the camber change. So, we’ll take a look at angle versus camber change.

First, we will reduce the angle at the left upper. Remember, we started out with 28 degrees of left upper control arm angle. If we change that to 24 degrees, what does the camber change look like now? We started with 4.0 degrees of camber and ended up, after dive and roll, with 1.3 degrees with the 28 degree upper angle. Now with 24 degrees, we have 1.25 degrees of dynamic camber, only a half a tenth loss. If we go to 36 degrees upper angle, we now see 1.42 degrees of angle, less loss, but only by a tenth or so.

With conventional setups, the left camber loss is hard to improve. But what about the right front? We’ll do some angle changes to see how much angles affect camber change.

We’ve already seen where an arm length change on the right front caused an angle change that helped to reduce the camber change. Let’s just keep the same arm length of 8.5 inches and change the angle. We started out with 12 degrees of right upper arm angle and the camber went from (-) 3.5 to (-) 3.9 degrees.

Now let’s go to 16 degrees. With the same dive and roll, we end up with (-) 4.8 degrees. We have gained 1.3 degrees of camber—not the change we wanted. Now, let’s go to 8.0 degrees of right upper angle. After dive and roll, we end up with (-) 3.0 degrees of camber, a loss of 0.5 degrees of camber—again not what we want. What we really want is zero change in camber.

If we put in 10.5 degrees of upper arm angle for this car, we get a dynamic camber of (-) 3.5 degrees, or zero change in camber, which is ideal for the tire. So, it seems we need to pay close attention to the right upper arm angle.

If we make changes to the length and bolt the arm back into the same height holes in the upper, the angle difference that change caused was the reason the car either turned better or worse.

The beauty of all this is, when we put those control arm angles into geometry programs, the moment center ends up well left of centerline, a position we have come to know makes the car turn better. Now we know why.

Conclusion – For more conventional setups, we need to think about our control arm angles. Take the information we have presented and think about how your car dives and rolls through the turns and then try to maximize your camber change by making control arm changes.

Much of the information we have presented over the years about roll/moment center design leads us to the most efficient camber change, because the arm angles that produce the optimum moment center location actually also produce much better camber change.

The post Changing Control Arm Angles: On Purpose or Not appeared first on Hot Rod Network.

Jackie Ward, 56, passed away after a two-car incident during the Southeast Limited Late Model Series Challenger Division 50-lap feature at Myrtle Beach (SC) Speedway Friday.

Ward, from Surfside Beach, S.C., was the owner of Grand Strand Towing and was a regular competitor at the facility.  Nearly 200 people gathered to remember Ward on Saturday morning at the Speedway.

All of us at Circle Track pass along our condolences to the family, friends, fans, and fellow racers of Ward.

More information: Myrtle Beach Online

The post Racer Passes Away After Myrtle Beach Speedway Incident appeared first on Hot Rod Network.

A lot of people think that there is a vast difference between dirt and asphalt race cars. And for the most part, they’d be correct. That is except for the evolution of the setups for both genres. If we study how each has evolved over the past twenty years, we can see a similar pattern.

Way back when I got seriously involved in racing technology, both dirt and asphalt cars ran tight setups to where a lot of load went to the right front tire through the turns. I was fortunate enough to get into the inner circle of both dirt Late Model racing as well as asphalt Late Models and Cup cars as well believe it or not. That’s a long story, but I was privy to some amazing insight.

At places like Daytona, the Cup and ARCA cars used the right front suspension way too much, I know because I was able to look at the shock travels of one of the top teams, a previous recent winner of the Daytona 500.

And the dirt Late Models were carrying the left front tire off the ground more times than not. If that tire is not on the ground, then all of the front weight of the car must be supported by the right front. And the dirt cars were sliding the corners hanging way out. Not so much the Cup cars and asphalt late models.

Some thought went into aero back then for both dirt and asphalt, but not like what has come to be. Both of these types came to know a lot more about how to use the air they were driving through to better advantage.

So, there you have it, things were not very efficient back in the day. But then in the late 1990’s and early 2000’s, things started to change for both dirt and asphalt. If I could explain it in as few words as possible and sum it all up it would be this. Dirt and asphalt teams started increasing the spring rate of the right rear springs, period.

Neither forms of circle track racing use the left front tire as much as was needed in the old days, so to speak. Once they started to balance the setups, the left front tire gained loading and traction. It then started to help turn the car and everything got better.

We have all come to know that if you can get a car to turn, dirt or asphalt, you can always find ways to gain rear grip. And that’s what happened. When the dirt cars stiffened the right rear spring, the cars started to turn much better, they kept the left front tire on the ground, and now they were searching for ways to gain rear traction where before they were tight/loose.

 If I could explain it in as few words as possible and sum it all up it would be this. Dirt and asphalt teams started increasing the spring rate of the right rear springs, period.

 The asphalt cars started running stiffer right rear springs too and gained use of the left front tire with the car turning more efficiently. They not only went faster but stayed fast longer. Teams noticed that the tires had less wear over the course of a race, they stayed cooler and the lap times dropped off less. Life was good, for those who got on the balance train early.

The coming together really hit a high note, and this might have been a beginning for the dirt teams, when Billy Moyer won both the Dream and the World 100 at Eldora in 1998 using basically an asphalt late model setup. It’s true and although I’ve talked about this in the past, it bears repeating. In that setup, the right rear spring was equal in rate to the left rear spring when most all of the time the dirt teams ran a softer right rear spring.

On asphalt too, especially in the upper mid-west, the asphalt teams ran softer right rear springs until Brian Hoppe kicked some serious butt in 1999 running equal rear, or even stiffer right rear spring rates. The evolution was getting started in a big way.

Now it is common to see much stiffer right rear spring rates in both dirt and asphalt race cars. This forces more load onto the left front tire which provides more front grip and a better turning car. Some teams overdo this aspect of setup and force too much load onto the left front, but that’s food for another story.

And, both dirt and asphalt teams learned that if they could get the front of the cars lower to the track, they could create more aero downforce and more free traction. Sure, aero drag went up some, but was easily overcome by horsepower, especially with the high HP dirt late models. The gain was in faster turn speeds.

If you look at modern day dirt and asphalt Late Models, the nose is on the ground, the cars are turning well and the dirt cars are driving more straight ahead. But there is more to the story. The dirt Late Models, asphalt Late Models and Cup cars are all utilizing bump setups.

Now the technology has finally come together in a way never imagined back in 1997, twenty years ago. Stiffer RR springs, lower noses, cars that turn well, and now everyone is running on bumps. What has the world come to?

So, to summarize my lead-in statements, this perceived vast difference in dirt and asphalt cars setups is no longer vastly different. In fact, they are more similar than different. Sure, the dirt cars still run with the rear hanging out somewhat, but that is mostly for aero flat plate affect that helps push the car towards the infield. And truth be known, some asphalt cars are utilizing the same effect, but you didn’t hear that from me.

I guess the final statement from me about all of this is, what works to help a car turn and what provides more speed is common among all race cars, be they dirt or asphalt late models, Cup cars or even Formula One. Making all four tires work just makes a car faster. And that is why when we present tech on race car suspension and setups, in many cases that tech relates to both dirt and asphalt. And that’s all I have to say.

If you have comments or questions about this or anything racing related, send them to my email address: chassisrd@aol.com or mail can be sent to Circle Track, Senior Tech Editor, 1733 Alton Parkway, Suite 100, Irvine, CA.

Dirt Modified Build

Bob,

I am a 70 year-old former Sprint Car driver who has not raced in over 35 years. As a devout reader of your tech articles, I think your thoughts and ideas could be a great help to me as I design and build a dirt Modified. My single desire is to campaign a totally “balanced” car, preferably a three link, four equal 5″ coil springs of maybe 500# each with 60/40  shocks, same size tires with 15# nitrogen in each, 302 SBF at 650HP on alcohol.

My goal is to work all four wheels WITHOUT lifting the left rear like a four-bar car. A friend who is an aero engineer at Boeing developed a computer model with the above design, using a 5.10 gear ratio on a 3/8 mile track that showed the car to be more than a little competitive. At my age I am more interested in being different than doing like everyone else. Do you think such a car could work? Springs in front, on top, or rear of the quick-change?

Your thoughts and comments would be greatly appreciated. Is it possible to buy a Shaw 4-bar chassis and set it up so the left side does not lift way up? front to rear scale weight 54% rear. Left weight 52%. Before wings I drove my sprint in the corners without sliding sideways. Even with wings I was still able to drive into the corners deeper before scrubbing off speed.

I am a strong believer in balance and gear ratio. Torque not HP is what makes the car go forward. Please do not laugh, this is a very serious desire to race on the National USMTS tour next year. Your help would be greatly appreciated.

Thank you, Dave Reidt

I would never laugh at anyone for their dreams. Many of the teams running the dirt mods don’t really understand the concept of balance. But, on dirt, we don’t always strive for complete balance due to the slick conditions later in the event. But, we do advocate making changes to bring the car from balanced, when the track has grip, to un-balanced somewhat to compensate for the slick track conditions. Running a whole event with the car perfectly balanced could be a problem, but who knows, you can certainly try that.

You stated that you wanted to run four equal rate springs on the four corners? That would not work very well to balance the dynamics unless your rear suspension is a swing arm design where the car feels about half the spring rate. But you were asking where to place the rear springs, so I don’t think that is the case.

So, that said, I’m not sure what your friend the aero engineer did to work out the balance, but running 500lb springs on the back of a three link won’t work to balance the chassis. The front would out-roll the rear and that car would be very loose.

I wrote a computer program 20 years ago that helped racers and myself develop a balanced setup and it has sold thousands of copies to dirt and asphalt racers without any complaints in all those years. I seriously doubt your guy could make that work knowing what I know then and now.

And, most teams have been getting away from high rear percent numbers and going with 52 – 52.5 percent max. The higher rear percent tends to make the car loose from unbalanced polar moment effect.

You should probably mount the rear springs behind the rear axle on both sides. Mounting on top has its problems when the rear end rotates, which it will always do to some extent and then the springs are not straight if mounted on top of the axle tube. And, you can setup a dirt modified, even a four-bar car, to have zero rear steer and not hike the left rear of the car.

In dirt modified racing, mainly the more successful drivers, are driving more straight ahead. When I ran karts on dirt years ago, that’s the way I drove and I could drive off and leave those who wanted to sling the cars sideways into the turns. I agree with that idea. And overall, I agree with the whole concept of your car.

Anti-Squat Questions

Bob,

Thanks for the thought provoking tech article on Anti-Squat.  I have gained a better understanding of three-point suspension.  Please explain how one figures out the percentage of A/S.

And I know you warned us no to go here but curiosity begs me to ask, if suspension angles were configured to go beyond 100% A/S, would the rear of the chassis rise up under acceleration, then drop under braking?

John

Yes, it would. Here is a good way to look at percent of anti-squat. If you produced a lifting force from the third link angle and rear end rotational force, that would displace all of the rear load, both the static load and that which transfers due to acceleration, then you would have 100% anti-squat.

This is very hard to calculate due to the variables of calculating the rear end rotational forces from engine torque and the loading at the rear from dynamic loading caused by load transfer under acceleration. You cannot do it with just link angles alone. Anyone who says they can is just barking at the moon.

 The rear end would lift if you exceeded 100% anti-squat. There is no real advantage to that because there is only so much load to use. You cannot create added load that is not there to begin with by going beyond 100% a/s. If you lift the front wheels off the ground under acceleration, like some sprint cars do, then all of the static front load is transferred to the rear axle and you have 100% load transfer of the front load to the rear.

The post Dirt Versus Asphalt Race Cars – The Great Separation appeared first on Hot Rod Network.

The ride height changes we see on a typical dirt car could be considered extreme. But, the movement of the chassis is necessary in order to position the car the way we want it to be. We can visually see how the car is reacting on the race track, but if we could view it up close at those attitudes, we could learn a lot more.

Similar to asphalt cars, “normal” ride heights are becoming a thing of the past. On dirt, the attitude of the car for the late models creates a lot of Right Front compression, Left Rear extension and a lot of associated rear steer at times.

But does all of that movement mean a team has to disregard ride heights when they setup the car? No. Ride heights will always be important, maybe more so now than ever, and we’ll tell you why.

We stress the importance of establishing a baseline for your setup. The term “setup” encompasses many different settings on the car. One of the areas of concern are the angles of the control arms, suspension links and positions of the moment centers, front and rear.

Every team needs to establish ride heights for their dirt car no matter which class you will run. This baseline height will dictate many of the other settings and going back to a known height will help you with changes you might want to make to the car from time to time.

 Why Ride Heights For Dirt Cars? – When we set the static control arm angles, we are depending on a certain chassis movement and that causes the dynamic angles to be what we expected. If we don’t keep track of our static ride heights and they end up changing, then the dynamic angles will also change.

Let’s say we make a spring change at the track. We either change the spring rate at one corner of the car, or we move the upper mount in or out on the chassis. These are common changes. If we don’t adjust the ride height back to where it was before we made the spring change, then our link angles will have changed too.

If we had good link angles before the change that produced just the right rear steer, etc., then after the change we will have something other than the ideal link angles. This can become very unpredictable.

A lot of things are dependent on the link angles for dirt late models and dirt Modifieds. Not only is the rear steer dependent on those angles, but the tire loadings for the four tires depend on those angles too. Here is why.

If the angles were such that the LR of the car lifted say 4.5 inches, and we changed the ride height so that the angles were less providing less lift, then we might only be up 4.0 or 3.5 inches. The rear steer of the car would change and the whole attitude of the car would be different. And the force of the LR tire driving forward will change and be less with less link angles.

The aero for a dirt car uses the top view angle created by the rear steer to produce a side force that counters the lateral force trying to push us off the track. This aero effect is called Flat Plate aero. The angle of the “flat plate” side of the car is critical in determining how much aero side force the car will produce.

With this flat plate aero, the angle can be too much, or too little. Once we find that perfect angle, the car works much better and it’s like we gained tire grip when it is really just aero side force holding the car onto the track.

Not only is side force present, but downforce from the front to rear angle of the car is pushing the car down. If the LR lift is diminished then we will have less top side angle to produce flat plate downforce and we then have less loading on the tires.

Less side force and less downforce could be a result of making changes to our ride heights. Sounds crazy, but all of this does matter. There is so little grip in a dry slick track that any help we can get could potentially drop our lap times by a tenth or two.

Static verses Dynamic Ride Height – So we have decided that it is good to establish static ride heights and to make adjustments to our ride heights when making spring changes so as not to change the link angles.

You can do practice spring changes in the shop and note how much you need to adjust the ride height back to the baseline. That way, a certain rate change in spring rate might need a 3 turn change in spring height at one corner of the car. Or, moving the RR upper spring mount in 3 inches might necessitate a 4 turn change in that springs height.

What about the dynamic ride height? We can measure the shock travels at all four corners, especially the LR and RF corners. Those two move the most of the four corners on the car. We can position the chassis at those ride heights when the car is in the shop and on a level surface.

With the car at the dynamic ride heights, we can physically measure the rear steer and the angle of the flat plate side from straight ahead. There is a reason why we need to note these angles.

With aero side force, there is also a lot of drag, but if we can drive through the corner faster and keep from sliding, then the drag is worth it in the long run. But if the track is tight with a lot of grip, we don’t necessarily need that side force as much, or not at all.

Then we can reduce the lifting of the LR, which reduces the rear steer and top view angle of the car in order to reduce the drag. Now we can accelerate much quicker down the straights and drive more straight ahead.

The tell tale for all of this would be the shock travel in the LR corner. If we could measure the travel in the shop verses rear steer, then once we hit the track, we could compare the shock travels and adjust the link angles until we read the shock travels we think we need for the track conditions.

Less rear steer and associated LR rebound shock travel for tacky tracks, and more rear steer and more LR rebound shock travel or slicker tracks. This is one more tuning tool we can use for dirt cars to help us adapt to changing conditions.

We know we need to make setup changes to adjust the balance for different conditions. Now we know we also need to make adjustments to the link angles so our dynamic ride heights will produce the degree of rear steer that is needed to gain or reduce aero side force and drag.

Conclusion – We have come to learn that dirt late models and modifieds are complicated engineering marvels. But that doesn’t mean we cannot use simple common sense to set them up. The two areas we need to concentrate on are levels of balance that match the track conditions of grip and the use of aero side force when the track begins to go slick to help hold the car in the turns.

When we study ride heights, both static and dynamic, we can then begin to understand more about what the actual attitude of the car is on the track. We can directly measure this angle and then know how to setup the car.

The post Controlling Suspension Travel in Dirt Cars appeared first on Hot Rod Network.

The tire loading for dirt cars is subjective and what you need is always dependent on the track conditions. What separates dirt cars from asphalt race cars, aside from the obvious, is the fact that grip on dirt tracks is constantly changing. That presents a huge problem.

What many don’t understand is that dirt Late Models and Modifieds are often setup much like asphalt Late Models and asphalt Modifieds when the track has a lot of grip.  At least they ought to be. So, setups for track conditions that offer less than a lot of grip are hard to plan for. Maybe the following technology can help.

Ideal Tire Loading – Just what is “ideal” tire loading anyway? On dirt, that changes, like we said along with the tracks grip. Ideally, we get more traction from an opposing set of tires (tires on the same axle so to speak) when they are equally loaded. But for dirt cars, when the track goes slick, that only makes the cars skate across the slick surface.

Just like on asphalt, we have what is commonly referred to as Weight Transfer with dirt cars. When we corner on a circle track turning left, the lateral forces will transfer some of the weight that was resting on the left side tires over onto the right side tires.

In a dirt race car, our setups determine where the weight that has transferred goes. We cannot just do a simple weight transfer calculation to know what our wheel weights will be for a particular car or set of conditions.

Ideal wheel loading on dirt is when the load transfer matches the conditions. If a balanced setup and “ideal” tire loading does not work for dry slick conditions, and we know it doesn’t, then how do we know what loadings will work?

If we had a measurement we could take that would equate to a degree of unbalanced setup that would be better for the “less than ideal” changing conditions, we could then plan out our setups in a more accurate way. We could get away from trial and error.

Finding The Right Loading – What if we could find, by measuring, the existing mid-turn loading on the four tires? That would take a lot of the guess work out of setting up our dirt race cars. There is a way to do that.

A fact we have come to understand about wheel loading on a race car goes like this, if you change the loading on one tire, then you have changed the loading on the other three tires. You cannot change one tires loading and not affect the other three tire loads, it just isn’t possible because there is only so much load to go around.

So, based on that fact, if we know what load is on one of those four tires we ride around on, then the other three tires will have to be loaded in relation to that tire we are measuring, right? Yes.

On a dirt Late Model or Modified, we will choose the Right Front corner to work with. Why? Because it is easy to get to, and with the front of the car, the load transfer is easy to calculate. In the rear of the car, there are two weight transfers going on, the transfer of the sprung chassis weight and also the transfer of the un-sprung rear end weight. Those happen separately and must be added together to get the total weight transfer.

OK, so now I know which corner I want to measure the load at, but how do I do that? We do that by measuring the loading, or force, on the spring. Simply put, if the tire supports a certain load, then the spring must put out a force at least large enough to support the car and that load. By spring, we mean the ride spring plus the bump device rates if those are in use.

Measuring Spring Force – If ideal tire loading is good for a tight dirt track, then some degree of less-than-ideal tire loading must be right for dry slick conditions. On a double A-arm suspension, the spring rate is translated out to the tire and we call this the Wheel Rate. This is old school stuff, but necessary at this point in the discussion in order for us to understand how to measure forces.

The wheel rate, for those of you who don’t remember, is calculated by measuring the motion ratio, squaring it and then multiplying it times the spring rate. Example: if our motion ratio was 0.75 (for every inch the wheel moves, the coil-over moves 0.75”), then squaring that would give us a number of 0.5625.

If our ride spring rate was 350 lb./in., we just multiply 350 x 0.5625 to get a wheel rate of 196.8 lb/in. So far, so good. Now, how much force does it take to support say 550 pounds of static RF weight? 550 divided by 0.5625 = 978. It takes 978 pounds of spring force at the coil-over to support the car. That is just to hold that corner of the car up at normal ride height.

Evaluating Corner Loads – The place on the track where we are concerned about tire loading is when the car is going through the turns, preferably mid-turn. I did some calculations that I won’t bore you with here, and at a normal medium banked track we could expect to transfer about 350 pounds of load from the Left Front tire to the Right Front tire at mid-turn with about 1.4 G’s on a 12 degree banked track in a 2350 pound dirt late model.

If our original static load on the RF tire was 550 and we transfer 350 pounds, then our mid-turn loading on the RF tire would be those added together, or 900 pounds. Using the same motion ratio squared number of 0.5625, the force the spring would need to produce to support the new tire loading would be 900 divided by 0.5625, or 1,600 pounds. This represents the spring force we need to produce the ideal tire loading for a tight track with lots of grip.

Now that we know the ideal spring force, we need to find what less than ideal is in spring force for those times when we are 90%, or 80% off of ideal with the track conditions. We can just multiply the inverse of those percentages times the weight transfer to begin to upload the RF tire. This causes the car to go towards a tight setup, one that we will need in varying amounts, to overcome the slick conditions.

If, say, we need 1,600 pounds of spring force for ideal grip, then we need to read a higher force if the track were say, 90% of ideal grip. We then take 0.90 and inverse (divide it into 1.0) that to a number of 1.11, Multiply 1.11 times the 1,600 pounds for ideal spring force and we should be reading somewhere close to 1780 pounds of spring force at the RF coil-over.

If the track were only 80% of ideal, then the inverse of 0.80 is 1.25 and our RF spring load should go up to 1.25 times 1,600 = 2,000. Remember that if the loading on one tire goes up, the other three will also change. The other diagonal tire load goes up and that would be the LR tire. As the LR tire load goes up, the two rear tires become more equally loaded and the car gains rear grip, something we need on dry slick tracks.

If you need to upload the RF corner to a higher spring force and tire load, you could do one of the following: 1) lower the J-bar or panhard bar, 2) decrease the RR spring rate, 3) increase the LR spring rate, 4) move the RR spring upper mount in, or 5) increase the packer spacing in the RF if running on bumps.

[CTRP-180500-DIRT-05] Of the many ways we can un-balance the car, moving the front mount on the four-bars up on the left side will drive the LR tire up under the chassis and force more loading onto that tire and the RF tire at the same time. Other changes include softening the RR spring rate, stiffening the LR spring rate, lowering the J-bar, and moving the RR spring top mount in towards centerline.

Summary – This provides us with an important lesson in modern dirt race car setup. Most of dirt history shows us that trial and error testing helps us to learn which way to change the setup when the track conditions change. Now we can get away from the trial and mostly error ways and begin to measure our setup balance in proportion to the track conditions.

This was just an exercise to show you how you can take measurements of the spring loading that can help you determine what changes to make to prepare for the changing track conditions. It will be up to you to decide what percent off of ideal to setup your car so that it will be good for the conditions.

These are exciting times for dirt car engineering and setup. Now we have a method we can use to work out setups and a way to measure the results. Have you measured your cars spring load forces today?

The post Weight Loads and Forces for Dirt Cars appeared first on Hot Rod Network.

For asphalt Late Model racing, ride heights are becoming a thing of the past. Many tracks and sanctions are relaxing the ride height rule because of the bump setups that cause the car to go far below the usual standard. But does that mean a team has to disregard ride heights when they setup the car? No way. Ride heights will always be important, maybe more so now than ever, and we’ll tell you why.

We stress the importance of establishing a baseline for your setup. The term “setup” encompasses many different settings on the car. One of the areas of concern are the angles of the control arms and positions of the moment centers, front and rear.

Every team needs to establish ride heights for their car no matter which class you will run. This baseline height will dictate many of the other settings and going back to a known height will help you with changes you might want to make to the car from time to time.

What Heights Do I Want? – For manufactured race cars, the car builder usually has established a set of ride heights for you to use. We would recommend using those ride heights because they are the basis for every suggestion for mounting points that the builder provides.

If you don’t have your ride heights established, or don’t know what to set them at, here are the tried and true heights that racers have used for years. The LF is usually the lowest corner and is set at 4.0” if the ride height rules have a minimum of 4.0” for any part of the chassis. You should cheat up 1/8” or even ¼” to make sure you don’t get thrown out of tech for a low car after the race.

Moving along, the RF corner is usually ¼” to ½” higher than the LF corner and the LR corner is the same. The RR corner is the highest at from 4 ½” to 5” in height. Like we said, these are tried and true ride heights. It doesn’t mean you have to abide by these numbers.

I think the traditional setups caused the most travel in the RR corner, and so that corner was set higher in ride height to compensate for that travel. With modern day setups using a much stiffer RR springs, the travel amount has gone down considerably. Where we used to see 3.5 to 4.0 inches of travel in the RR, we now see 2.0 – 2.5 inches or less.

With the RF traveling 3.0 – 3.5 inches, we will still have a rake in the attitude of the chassis even if we level out the right side ride heights. Then the rear of the car will be a good ½” lower which lowers the overall race car Center of Gravity.

Which Settings Are Depend On Ride Height? – Once we establish our ride heights, we need to establish certain chassis settings in relation to those ride heights. We might have recorded heights off the floor for things such as, the lower control arm chassis mounts for the front end. We might have set our front trailing arm mounts in the rear suspension by using measurements off the floor. We need to re-think those measurements now.

If you haven’t thought about it before, when making setup changes, like going from conventional setups to bump setups, all of the angles will be much different for the control arms and suspension links. Angles that worked before now don’t work very well.

Some of the frustration you might be having with the new setup could be traced to improper link angles. For example, if we might have always set the RR trailing arm angle at 4.0 degrees because the RR shock travel was 3.5 to 4.0 inches. When the travel changed to under 2.0 inches, that angle must also change to under 2.0 degrees or you’ll end up with a lot of loose rear steer.

With the new stiffer RR spring rate, the high angle pushes the RR wheel back and the front mount won’t travel enough to bring the RR wheel back to its static position and the wheel will stay back some amount steering the rear to the right.

The overall travel in the rear will diminish also. So, any angle you put into the LR link to help produce rear steer under acceleration and squat won’t produce the same effect. You might need to put more angle in that link to compensate for less movement.

Front Considerations For Ride Height – At the front, we have some exciting things to think about. For the conventional setups, life goes on as usual, but for the bump setups, we might be able to rethink how we always did things.

We all know by now that the front geometry is important and that it dictates the control arm angles in the AA-arm suspension. What we have established through testing is that the ideal control arm angles will produce less camber change to keep the contact patches consistent.

One fact about bump setups is that the chassis moves very little vertically, or in roll for that matter, when the front is on the bumps with their very high spring rates. So, in that very small window of movement, if we set control arm angles that will produce very little, or no, camber change, our cars should like that, and they do.

If we put the car at the on-track ride height and then study the camber change, we might re-think our control arm angles, at that height. If we make changes, then when the car is at the higher static ride height in the shop or in the pits, the arm angles will look much different, but why do we care about that. All we really care about is where the angles are when on the track and on the bumps. Those setups must stay on the bumps in order for this to work.

Experimentation – I did a little experimentation with control arm angles and ride heights. Here is what I found out. This was really interesting. I took a typical asphalt late model front AA-arm geometry layout like we use on the current bump setups and noted the Moment Center location at ride height and again at 3.5” of dive and 1.0 deg. of roll.

The upper control arm angles are: Left Upper at 28 deg. and the Right Upper at 12 deg. and the Left Lower angle is 2.5 deg. and the Right Lower angle is at 1.5 deg. At ride height, we have a MC height of 3.2 and a width of negative 13.1” (left of centerline). When I dive and roll this car, I get a MC of 1.0” in height and 13.1 inches to the right of centerline.

In our research, the upper control arm angles that produce the least camber change put the MC to the left of centerline, much like our static MC. But with the MC location after dive and roll, the car ends up with the worst angles for camber change. So, any movement of the car vertically will end up causing a change in camber the car won’t like.

What I end up with is this, what if I put the car at the attitude it will be racing at, down on the bumps, and then set the same upper control arm angles as they were in the example at ride height? What if down on the bumps I set the LU angle at 28 deg. and the RU angle at 12 deg.?

The lower angles cannot be changed due to the clearance between the lower ball joint and the wheel, plus there is no room to raise the inner chassis mounts. Now, with just these upper arm changes, won’t my camber change be much better? Yes it will.

As to camber change while on the bumps, a quarter inch change in ride height, from 3.5” dive to 3.75” dive with the old system yielded a 0.8 degree camber change in the left wheel and a 0.6 degree change in the right wheel. That’s a lot for that small a ride height change. On the other hand, with the new upper angles, the left wheel only changed 0.2 deg. of camber and the right wheel didn’t change camber at all. I think we are on to something here.

Another interesting thing about this test is that the MC height was 1.0 inch above ground originally and went to 7.4 inches below ground with the new upper angles.  We know that the height of the MC is directly related to chassis stiffness, so a longer moment arm would make the front more efficient, making it turn better.

Conclusion – Ride heights are important in keeping track of our link angles and keeping everything consistent. But could we now look at the ride heights in context to how we race the car? It’s food for thought.

The post Asphalt Ride Height Tech appeared first on Hot Rod Network.

We’ve done articles on how to refresh your asphalt race car after a long and tough season. We have told you how to tear the car down, how to inspect it, paint it and how to re-assemble it so that it is like new. This piece is not about that. This is all about setups and what you can do to make your car more competitive.

When this goes on our website and facebook page, it will be in December and when it is in print in the magazine, it will be near the beginning of the season. Right now, as we prepare to attend PRI, the premier racing trade show in the country, now would be a good time to take all of this in and assemble a Christmas list of parts and pieces you might need to become more competitive.

Approach and How To Re-Think – The first place to start with your setup re-thinking process is re-thinking your current thinking process. I run into a lot of teams that just plain frustrate me because they cannot get their thought processes right. This race car setup thing is not as hard as most teams think. They either think too little, or over-think it.

It doesn’t need to be that way. There are basics that must be adhered to and there are tricky ways to give the car what it wants. But even those are not hard to understand or apply. What might help is to just make a list.

What a list does is take away much of the confusion in a process that has a lot of parts, and admittedly, setting up and maintaining a race car has a lot of parts. I make lists all the time. It helps me stay organized. If you look at each part individually, there’s not much to them and they are easy to understand and work with. But if we try to take it all in at once, it sometimes overwhelms us.

The list should break down the processes you will use to setup your car. When you make the list, write down all of the processes you go through for your car and your type of racing. Then after you think you have everything listed, put a number beside each one in order of importance and in the order of when they should be addressed.

Then re-write the list in that order preferably in a Word document or similar computer file so you can print it out. You can provide a copy to each of the team members and split up the duties among yourselves.

Key Areas For Performance – We will assume that you have the basics taken care of and that the car is in good working order. This is all about setup and the primary parts that make up a good setup.

The part of the race track we design our setup for is the turns portion. This is where setup matters. We setup for mid-turn first, and then tune the car for entry and exit without disturbing the mid-turn setup. The reason why we do mid-turn first is because when we make that part of the track correct, our entry and exit will often get better too. So here goes with mid-turn.

First off, we want our weights to be properly distributed on the four tires at mid-turn. There are two things, and two things only, that will make your car fast through the middle. One is proper load, or weight, distribution on the four tires and second is having the greatest contact patch size possible for your tires on your type of race car.

That sounds too simple, right? It is and it isn’t. Getting that perfect distribution of weights and getting that perfect tire contact patch takes some effort, but there are no tricks. Just simple, common sense, practical methods.

As to the first item, springs, bumps, sway bars and moment centers are what influence where the weights will go among the four tires at mid-turn. When we get this right, we call that the dynamic balance. Here are facts about the parts that affect the mid-turn performance:

• Making changes to the spring rates at one corner will affect and change the weights on all four corners.
• Raising the panhard bar (rear moment center) will upload the Left Front tire and Right Rear tire, and unload the Right Front tire and Left Rear tire.
• Increasing the RR spring rate will upload the LF tire and RR tires, and unload the RF tire and LR tires and loosen the setup. Decreasing the RR spring rate does the opposite.
• Increasing the LR spring rate will upload the RF and LR tires and unload the LF and RR tires and tighten the setup. Decreasing the LR spring rate does the opposite.
• The roll stiffness of the front suspension must be equal to the roll stiffness of the rear suspension in order for the weight distribution to be correct at mid-turn. There are several influences that affect roll stiffness, not just the spring rates.
• For circle track cars turning left, increasing the left upper arm angle and decreasing the right upper arm angle will produce a better contact patch by reducing camber change. This is a generalization, but represents knowledge that has come about over the past twenty years. There is an optimum angle for each upper control arm.
• There is a specific degree of camber and tire pressures in each front tire that will produce the largest contact patch. Finding the best camber and pressure is accomplished by the use of a tire temperature gauge and a tire pressure gauge.
• Large (over 1 3/8” in diameter) sway bars are a thing of the past. Large sway bars reduce roll, but cause excess weight transfer and upset the load distribution of the car. Roll in a racer car is not a bad thing.
• Very stiff springs and bumps are controlled with very stiff rebound settings in the shocks. This is not “tie-down”, just control. That is the job of the shocks, to control the spring rate.
• The static weight distribution (represented by cross weight) will dictate what weights end up on the four tires at mid-turn after the loads have transferred. For each car, there is a specific static weight distribution that will produce the ideal weight distribution at mid-turn once the setup has been balanced.
• The front to rear weight percent dictates the ideal cross weight the car will need for proper static weight distribution. Increasing the rear percent necessitates an increase in the cross weight percent in order to remain neutral in handling. Decreasing the rear percent requires the opposite.

All of these facts concern mid-turn setup. They also relate to the transitions, but we cannot change these in order to tune the transitions. We have to use other methods.

Reading The Tire Temperatures – The primary way to evaluate your setup is through the reading of the tire temperatures. These temperatures tell how much work a tire is doing and somewhat relates to how hard it is loaded.

• Generally speaking, if the averages of the two rear tires are hotter than the averages of the front two tires, the car is loose and needs more rear grip.
• If the LF tire is cooler than the LR tire, then the setup is tight and the front roll stiffness is greater than the rear roll stiffness.
• If the LF tire is hotter than the LR tire, then the setup is loose and the front roll stiffness is less than the rear roll stiffness.

We have to be careful when reading the tires because there are influences that can cause higher than normal tire temperatures that we might mistake for setup problems. If a car is setup with too much rear grip, it will be tight in the middle and then usually loose off the corner. The RR tire might spin as it goes loose off the corner and heat up.

That is why we evaluate the left side tires. This can tell you if the setup is loose or tight. The tight/loose syndrome confuses this issue.

Adjusting Tire Pressures – Tire pressures dictate much about the footprint, or tire contact patch size. If the tire pressures are too low, then the middle of the tire will be less loaded than it could be. If the pressures are too high, then the middle of the tire will be overworked and the outer parts of the tire will be less loaded than they could be.

When reading tire temperatures at the usual three positions across the face of the front tires, the middle temperature should be the average of the two outside temperatures. If we read 175 outside, 190 middle and 205 inside, then the tire has the right pressure because 190 is the average temperature of the three.

At the rear, we seldom see the same temperatures across the face of the tire. So, we also try to get a middle reading that is an average of the three temperatures.

Setup For The Transitions – Now that we have the middle setup corrected and tuned, we need to concentrate on the entry and exit portions of the track. We will work with parts of the race car that are not involved in the mid-turn setup list. Items like springs, bumps, sway bar size, panhard bar settings or weight distribution cannot be changed once the mid-turn setup balance has been achieved.

Read that last paragraph over again and again until you memorize it. We won’t be changing any of those items as we tune the transitions. So, what do we work with? We work with shocks and mechanical influences. Here are some facts related to transition tuning:

• At mid-turn, we have what we call a steady state condition where the shocks are not moving. If shocks are not moving, then they are not influencing the weight distribution.
• Making a shock change on one corner will affect the weight distribution on all four tires when the shock is moving during entry or exit.
• Increasing the compression rate of a shock on the front will load that corner and the diagonal corner while braking and while the shock is moving. Decreasing the compression settings will do the opposite.
• Increasing the compression rate of a shock on the rear will load that corner and the diagonal corner on acceleration while the shock is moving. Decreasing the compression settings will do the opposite.
• Increasing the rebound rate of a front shock will decrease the loading on the tire on that corner as well as the corresponding diagonal tire while the car is accelerating and the shocks are moving on exit.
• Increasing the rebound rate of a rear shock will decrease the loading on that corners tire as well as the corresponding diagonal tire while the car is decelerating and the shock is moving on entry.

If we get the mid-turn handling balance correct and the loading on the four tires correct, then entry and exit performance using light braking and a soft throttle should also be correct. It is when we brake hard, or accelerate hard that problems come in to play.

If we think about what is happening with those actions, we can then create solutions. The fact is, we can only do so much with shocks. And we can never solve driver induced problems like over-braking on entry or using too much throttle on exit and overloading the tires. There are limits to what the car is capable of.

So, if there are limits to what can be accomplished using shocks in the transitions, then what else can we do? Most of driver complaints involve needing more bite off the corners. More bite means the driver can get on the throttle earlier and use more of the throttle. Here are some tips for creating more bite off the corners:

• Rear steer to the left is the most effective way to increase rear grip off the corners.
• Using flexible link bushings on the RR suspension links will loosen the car on entry during braking by causing rear steer to the right. (Hint: Metric stock class cars)
• Using flexible link bushings on the RR suspension links will tighten the car on exit during acceleration by causing rear steer to the left. (Hint: Metric stock class cars)
• For cars with three link rear suspensions with angled top view outer links, setting the panhard bar with the right side higher (right side chassis mount) will push the rear end left and steer the rear to the right through mid-turn, helping the car to turn.
• For cars with three link rear suspensions with angled top view outer links, setting the panhard bar with the right side lower (right side chassis mount) will pull the rear end to the right and steer the rear to the left through mid-turn, making the car tighter.
• Using more link angle (front higher than the rear) in the LR suspension link will push the LR tire back if the car is allowed to squat (less anti-squat) on acceleration from weight transfer to the rear, which will tighten the car on exit.

Measure Of Performance – Once we solve the transitions, the car should be good to go and have plenty of performance, at least through the turns. But how do we know how good we are? There is a simple and effective way to measure your setup performance.

We race against other cars in our class at our race track. So, if we are trying to measure our setup performance, we measure our elapsed times just while the car is turning. We can pick a point on the track at entry and another point on the track at exit and time that segment. Then we compare our times to those of the competition. We want to at least be as fast, if not faster than the other fast cars.

Then we compare our whole lap times to the lap times of the other cars. If we are faster than the competition and our corner times are the same, then we have better acceleration.

If our turn times are as good or better than the competition, and our lap times are slower, then we need to look at our motor combination to try to find more acceleration. If our turn speeds are good and the lap times are off, it makes sense that the problem is with motor or gear deficiencies.

Taking turn segment times is more important than lap times because it will tell you directly if your setup is working or not. It can help you concentrate on where your performance is lacking quickly. I have always taken the turn segment times for cars that I am working with at the track. If my segment times are fast, then I have done my job.

Gearing The Race Car – The last part of on-track performance is in the gearing. This is an item you can change at the track. The motor is not. If we are lacking straightaway performance, then we need to look for ways to improve acceleration.

Some teams think lower gearing helps acceleration. Running a lower gear (higher number) does not help you accelerate if that gear puts the RPM of the motor out of the torque peak and horsepower range.

Torque is what gets us off the corners. The torque curve lags behind the horsepower curve in that we peak in the torque curve sooner in the RPM range than when we peak in the horsepower range.

I have had teams tell me that they dropped down from a 5.60 gear to a 5.10 gear and gained a couple of tenths. That represents a 600 RPM drop when running a top speed of 6500 RPM. For lower horsepower motors like the common crate motors, we can easily gear ourselves too high and go beyond where the motor makes good torque and horsepower.

Remember, a lower gear and higher RPM does not get us off the corner faster if that puts us out of the RPM range of power for the motor we are using. Look at your engine dyno graph to see where the motor is making the most torque and adjust your gearing to effectively use that power.

When you experiment with gearing, make a large change in gearing so you can see quickly if you are moving in the right direction. Then fine tune the gear ratio for maximum acceleration.

Conclusion – If you can follow along with these suggestions, you can easily fine tune your setup and your lap times should get much better. If all of this doesn’t help you match the speeds of your competitors, you might just be down on horsepower or in need of basic engine tuning.

With the method of turn segment timing we discussed, don’t forget to take into account the age of your tires verses the other cars tires. If the same, you can evaluate your setup and if you are as fast or faster than your competition through the turns, you can look elsewhere for what is causing you to be slower in lap times.

Sources:

Afco Racing
www.afcoracing.com
800-632-2320

Allstar Performance
www.allstarperformance.com
269-463-8000

Coleman Racing
www.colemanracng.com
800-221-1851

Day Motorsports
www.daymotorsports.com
800-543-6238

Gale Force Suspension
www.galeforcesuspension.com
251-583-9748

Integra Shocks and Springs
www.integrashocksandsprings.com
800-472-3464

Landrum Springs
574-353-1674
www.landrumspring.com

Online Racing School
www.onlineracingschool.com
386-677-5384

PitStopUSA
www.pitstopusa.com
866-722-3432

RE Suspension
704-664-2277
www.resuspension.com

Smileys Racing Products
www.smileysracing.com
866-959-7223

The post New Season Performance: Making A Slow Car Into A Fast Car appeared first on Hot Rod Network.

Discussing port volumes as a measure of evaluating potential engine performance.

Over time, we’ve used this column as a forum to discuss various aspects of engine air flow. One topic we’ve not included in these discussions has been the practice of comparing port volumes as a measure of evaluating potential engine performance. The following addresses how we feel about that yardstick for making comparisons.

First of all, air flow benches are nothing magical. They can be valuable but their limitations need to be recognized if the data they produce is to be of any value. In other words, a gain in air flow (in and of itself) will not always result in a corresponding gain in power.  What these benches can provide is a stepping stone in determining the potential for an increase in power.

For a number of years, Harold Bettes and I have been friends.  Both of us attended the University of Texas, having majored in mechanical engineering.  Harold spent many of his career years in this industry working for and helping develop air flow measurement equipment for the Superflow Corporation.  Consequently, he is well versed in the subject.

In his view, knowing air flow data and how to properly use it can be helpful when making choices about a variety of engine and powertrain components, including rear gear ratios that can be linked to inlet airflow data since peak power typically occurs at or near peak air flow.  Here’s an example of what that can mean.
On the assumption that air flow data was obtained at a flow bench depression of ten inches of water, that ignition spark has been optimized, air fuel ratios and volumetric efficiency are maximized along with combustion efficiency, a fairly accurate power estimation can be calculated as tied to the air flow data.  The following is an example of that approach.

Let’s say we have a flow bench reading of 200 cfm as applied to an eight cylinder engine.  The equation that follows is:

200 cfm x 0.43 = 86 x 8 cylinders = 688 hp @ peak power rpm.

However, if all the air flow data had been measured at 25 inches of water bench depression, the multiplier would change to 0.27 instead of 0.43, resulting a calculation of 432 hp at peak power rpm.  If we wanted to calculate the rpm at which these estimated peak power levels would occur, a comparable mathematical approach can be used.  That equation would look like:

Rpm for peak power = 2000/43.75 x 156 cfm = 7,131 rpm

In my discussions with Bettes, he pointed out that this approach makes the assumption that all air flow data is obtained using a “full” intake system that includes carburetor, intake manifold, and cylinder head to be used on the running engine.

Now, you may ask, why is air flow quality so important?  We’ve previously touched on this, but a few of the points bear emphasizing.  For example, consider both air and fuel behave much like a compressible fluid.  That is to say they can be compressed by each differs from the other on how they behave when subjected to greater or less than atmospheric pressure.  Maybe the best way to discuss this is as follows.

Essentially, air is a compressible fluid.  It exhibits the properties of a compressible fluid because it has viscosity that increases as a function of its flow rate (velocity).  But air also tends to “stick” to the surfaces over which it passes (inlet passages, etc.).  Even if efforts are taken to create either stable or controlled air flow conditions (swirl, tumble, etc.), it remains as the “working fluid” by which fuel is delivered to the combustion space.  It thus becomes of value to understand some of the aspects (including benefits) of how air flow quality and quantity, especially quality.

In this regard, we can return to the air flow bench for ways to get a sense for both stable and unstable inlet air flow.  We’ve known some long-time flow bench operators who claim they can judge the efficiency of a given port by the sound of air.  That is to say the less “noise” the port exhibits the more efficient it will perform.  We prefer something more concrete than that.  For that reason we’ve always relied on the use of various pressure probes (hand-held is sufficient) to locate and quantify trouble spots in the inlet path.

There are two such probes that have proven beneficial over the years of personal use of a flow bench.  One we’ll call a “velocity probe” which consists of a straight, short-length of tubing of about 0.020” i.d. connected (usually with a length of plastic tubing attached to the down-stream side of a bench’s flow measurement) and the other a section of the same size tubing bent into a U-shape at its open end and connected to the same part of the bench’s measuring system.  (We’ve included a sketch to illustrate the shape and location of use in a typical intake port passage, just for orientation).

The so-called “J-probe” will help identify areas where there is a potential boundary layer separation between the air and surfaces over which it is passing and the possibility of air/fuel ratio disruption and lost combustion efficiency (power). Don’t be surprised if the J-probe measured manometric data registers less than atmospheric pressure. That’s because it’s exhibiting turbulence that’s counterproductive to maintaining the desired net air fuel rations eventually in the combustion space.  Once you’ve “smoothed” out the air flow this condition should be notably reduced.

Flow path surface texture is yet another factor that can have an effect on both flow quantity and quality.  This is especially true on the intake side of the overall flow path where atomized fuel needs to be kept in suspension, even in port-injected applications.  There is sufficient opportunity for mixture quality to be diminished from the point of fuel introduction to the time of spark ignition than to overlook the chances to improve the way it is blended with the air.

For example, while you may discover ways to “polish” the intake path to increase dry air flow, it does not necessarily follow that such conditions will not decrease the ability to keep fuel in suspension.
All this is to say that there are numerous factors that play into increasing an engine’s net air flow than “more is always better.” Keep in mind that you need to strive to creating and maintaining the proper blend (including mixture quality) as air flow is increased, because it is in the combustion space that “the proof is in the pudding.” Admittedly, that may be a bit out of place for CT but, in fact, it’s true.

By the way, you’ll note that at no point in this month’s discussion did we reference anything and port volumes as measured in cc’s.  ‘Nuff said.

The post Enginology: More Thoughts on Engine Airflow appeared first on Hot Rod Network.

The Need to Manage Our Weights

It was discovered a long time ago that what makes a race car fast is helping the tires to do as much work as possible. The two things we have learned about making tires work is that they need to be loaded, the more load the more traction. And they need a large tire contact patch to make all of that load grip the track.

What we will discuss today is the loading part of that equation and more specifically how to measure the loading. And as the title says, this is about asphalt race cars. We wrote a whole separate piece about dirt car loads just so the two camps won’t get confused. It just works better that way for me and the racers.

Ideal Tire Loading – Just what is “ideal” tire loading anyway? On asphalt, we get more traction from an opposing set of tires (tires on the same axle so to speak) when they are equally loaded. Elementary race car engineering tells us that in the real world, these opposing tires will never have the same loading when going through the turns.

The un-equal loading is caused by what is commonly referred to as Weight Transfer. When we corner on a circle track turning left, the lateral forces will transfer some of the weight that was resting on the left side tires over onto the right side tires.

A good example of that is when we corner too fast in a car with a high center of gravity, it tips up onto two wheels. That represents 100% weight transfer, and all of the weight must be supported by the outside tires because they are the only ones on the ground.

In a race car, we don’t tip up on two wheels, but we do get lighter on the inside tires and have more load on the outside tires when going through the turns. Here is the kicker. Our setups determine where the weight that has transferred goes. We cannot just do a simple weight transfer calculation to know what our wheel weights will be for a particular car.

Ideal wheel loading only happens when: A) the front and rear suspensions are working together in sync, and B) when we can manipulate the static tire loading so that the weights end up being ideal.

There is a lot to take in with that last paragraph. Let’s go over each scenario. For “A”, if the two suspensions are working together in sync, then the weight transfer can be calculated using relatively simple equations. But first, we have to make sure the static distribution of loads is correct so that the dynamic loading will also be correct.

With the “B” scenario, the two ends are not in sync, but if we play around with the static weight distribution enough, we can find by trial and error a weight distribution that will make the car neutral in handling. The two suspension systems will still be un-cooperative with each other, but at least for the time being, the car will be neutral in handling.

Finding The Right Loading – What if we could find, by measuring, the existing mid-turn loading on the four tires? That would take a lot of the guess work out of setting up our race cars. There is a way to do that.

A factual premise about wheel loading on a race car goes like this, if you change the loading on one tire, then you have changed the loading on the other three tires. You cannot change one tires loading and not affect the other three tire loads, it just isn’t possible because there is only so much load to go around.

So, based on that fact, if we know what load should be on one of those four tires we ride around on, then if we can get that tire loaded correctly, then the other four tires will have to be loaded correctly, right? Yes.

If I had to pick a corner of the car to work with along these lines, it would be the right front. Why? Because it is easy to get to, and with the front of the car, the load transfer is easy to calculate. In the rear of the car, there are two weight transfers going on, the transfer of the sprung chassis weight and also the transfer of the un-sprung rear end weight. Those happen separately and must be added together to get the total weight transfer.

OK, so now I know which corner I want to measure the load at, but how do I do that? We do that by measuring the loading on the spring. Simply put, if the tire supports a certain load, then the spring must put out a force at least large enough to support the car and that load. By spring, we mean the ride spring plus the bump device rates.

Measuring Spring Force – I hope you are following along with me on so far, because this may be the most important thing you will learn in your racing setup career. The spring rate is translated out to the tire and we call this the Wheel Rate. This is old school stuff, but necessary at this point in the discussion in order for us to understand how to interpret forces.

The wheel rate, for those of you who don’t remember like me, is calculated by measuring the motion ratio, squaring it and then multiplying it times the spring rate. Example: if our motion ratio was 0.75 (for every inch the wheel moves, the coil-over moves 0.75”), then squaring that would give us a number of 0.5625.

If our ride spring rate was 200 lb./in., we just multiply 200 x 0.5625 to get a wheel rate of 112.5 lb/in. So far, so good. Now, how much force does it take to support say 650 pounds of static weight? 650 divided by 112.5 = 5.78. That times the spring rate equals 1,155 pounds of spring force at the coil-over. That is just to hold that corner of the car up at normal ride height.

Evaluating Corner Loads – Where we are concerned about tire loading is when the car is going through the turns, preferably mid-turn. I did some involved calculations that I won’t bore you with here, but at a normal medium banked track, we could expect to transfer about 500 pounds of load from the Left Front tire to the Right Front tire at mid-turn with about 1.8 G’s on a 12 degree banked track in a 2800 pound Late Model.

If our original static load on the RF tire was 650 and we transfer 500 pounds, then our mid-turn loading on the RF tire would be those added together, or 1,150 pounds. Using the same motion ratio squared number of 0.5625, the force the spring would need to produce to support the new tire loading would be 1,150 divided by 0.5625, or 2,044 pounds. This represents the ideal spring force we need to produce the ideal tire loading.

Now that we know the ideal spring force, we can tell if we have too much, or too little force on our spring at mid-turn. If we measure the shock travel of the coil-over, and try not to overload it by heavy braking on entry, then we can put that coil-over on a force measuring machine. We then compress it to the mid-turn length that was recorded with the travel indicators and just read the force.

If, say, we need 2,044 pounds of spring force, and we are reading 2,400 pounds of force, then that tire is supporting more than it should be if the original weights were correct and the setup was balanced.

If we trust our original static weights, then we can make changes to the setup to change the loading on the RF spring, which translates to the loading on the RF tire. Without going into a lot of detail why, we’ll tell you a few ways to unload, or upload, the RF tire.

If you need to unload the RF corner, to a lower spring force and tire load, you could: 1)  raise the panhard bar, 2) increase the RR spring rate, 3) decrease the LR spring rate, 4) reduce the packer spacing in the RF if running on bumps, or 5) increase the packer spacing in the LF shock if running on bumps.

Summary – If you have paid attention, you have just learned an important lesson in modern race car setup. There have been ways to find a balanced setup by using software programs, and those are still around. But now you have a way to physically measure the on-track loading of your tires by using the spring force method talked about here.

Even when we had the luxury of predetermining setup balance using computer programs, there was always, and still is, a certain amount of uncertainty about the center of gravity height for a car as well as the actual G-force the car was experiencing.

Those are necessary and somewhat subjective entries in the programs, but now we can back up those calculations with real track force load readings. It’s a whole new day folks. Have you measured your spring/bump load forces today?

Sources:

Afco Racing
www.afcoracing.com
800-632-2320

DRP Performance Products
www.drpperformance.com
888-399-6074

Gale Force Suspension
www.galeforcesuspension.com
251-583-9748

Intercomp Racing
www.intercompracing.com
800-328-3336

Longacre Racing Products
www.longacreracing.com
800-423-3110

The post Weight Loads and Forces for Asphalt Cars appeared first on Hot Rod Network.

When I learned that my friend needed help setting up his dirt hobby stock car, I jumped at the opportunity. This little project allowed me to apply some of the technology we provide in CT to a car with limited adjustment capability.  Once we got into the car, I was surprised by our discoveries. What we do to this car can also be done to a Street Stock or similar type of car.

The problem with this car that was had built late last season was that it would not turn well and as a result would push on entry and go loose on exit. There are probably a few thousand or more teams in this country that have the same problem. So, I saw an opportunity to jump in there, do an evaluation to try to fix it.

The car is a 1985 Monte Carlo and has the metric four-link rear suspension, a stock frame throughout and must use stock type springs in their original positions. The shocks are mounted in the stock positions and the car has retained all stock suspension parts.

As with most “stock” classes, teams are allowed to trade stock pieces from other model year cars as long as the brand is the same. This class also runs large Hoosier racing tires all around where-as the street stock classes are only allowed one racing tire on the RF.

Breakdown – The first order of business was to weigh the car on the scales and measure and record the ride heights and the spindle heights for future reference. We wanted to maintain the original ride heights after installing new springs so the geometry would be the same and we needed to know the spindle height so we could check for proper clearance and make sure there was no bind of the ball joints while the car was on jack stands.

We then proceeded to break the car down and remove the springs and shocks to see what we had.  To get the front springs out, we had to remove the upper ball joints. This gave us a chance to inspect everything up close. My helper, Kenny Hellyer, was very familiar with the mechanics of these cars and was a definite asset in all of our re-design work.

The first problem we noticed was that the shocks on both sides in the front were rubbing on the inside of the height adjuster that was put into the car not to jack weight, but to create the ride height that was necessary to avoid bottoming out. The rear of the car had legal spring height/weight jacking, adjusting bolts.

The shock contact was so bad that one shock was leaking and both housings were bent severely. These were aftermarket twin tube shocks and still seemed to be working. I tried the standard method of checking them by placing one end on the floor and pushing in from the top. The shocks were so stiff that they barely moved.

I don’t know if someone chose really stiff compression numbers or if the shocks might have been bent, but these units were not helping the situation. On dirt, we must have shocks that will allow the car to run over the holes and bumps and move fairly easily. They must control the springs, but not be so stiff as to cause the tire to skip or bounce.

Front Geometry – I inspected the front geometry and noticed that the car builder had used the taller Impala spindles which reduced the lower control arm angles. He also had lowered the upper control arm mounts to gain more upper control arm angle. Both of these changes are highly recommended for this class. Using taller spindles actually improves both upper and lower arm angles.

The geometry I saw looked a lot like previous cars I have fooled with in the stock classes and I knew the moment center was close to where it needed to be, at or very near the centerline of the car. Had this work not been done, we could have expected the MC to be somewhere outside the car making the front end overly stiff.

The cambers were not what I would have expected or chosen. The LF was a little less than one degree and the RF was around 5 degrees. This is typical of a car that transfers a lot of load to the RF as that tire is forced to carry most of the front load and work hard to turn the car. The LF doesn’t need camber because it isn’t working very hard anyway. We needed to make camber changes to reflect how the front end would work after the redesign.

We reset the cambers to a positive (+) 2.0 on the LF and minus (-) 3.5 at the RF. Once we re-spring the car to allow a more balanced setup, the LF tire will definitely be working harder and take some of the load off of the RF tire. So, we would end up needing more LF camber and less RF camber. Our tire contact patch will be optimal with these changes.

Inspection of the caster settings revealed that the RF caster was in the negative range (upper ball joint forward of the lower ball joint) and the left side was positive. That would cause the steering to want to turn right, maybe good for sliding the car through the turns, but we were going to make this car turn well, so I opted for a different plan.

We moved the right upper ball joint back to create about two degrees of positive caster and that matched the left side caster. This way, the steering would be neutral and the driver could steer both directions without feeling a difference in resistance.

We were a little worried about possible binding of the ball joints with the increased upper control arm angles. So we cycled the spindles beyond what they would see on the track and found we had plenty of clearance. Always check to see if there is any binding or tightness in your suspension while you have the springs and shocks off the car.

Spring Rates – We next checked out the spring rates that were installed in the car. The fronts were marked as: LF = 1100 lb./in. and the RF was 1200 lb./in.  The front springs had a half round of the coil cut off, so the actual rate, although we did not measure them, was obviously higher than they were marked.

The rears springs were: LR = 225 and the RR = 150.  The rear had too much spring split, even for a Metric 4-link rear suspension with a high roll center. With the front spring rates being so high, this combination in the rear caused a lot of load to transfer to the RF on entry and through the middle of the turns overloading that tire. That would definitely help cause a push.

After careful consideration, we installed the following springs: LF = 900, RF = 850, LR = 225, and RR = 175.  The front reverse spring split with the softer RF spring helps corner entry and promotes front roll angle while the reduced spring split in the rear facilitates the high Metric moment center to help control the rear roll while not going too far.

Here is a further explanation of this.  For a balanced setup, we need for each end of the car to desire to roll to about the same angle in the turns. We have discussed this concept many times in Circle Track. A high rear moment center reduces the desire to roll, so if we don’t soften the RR spring, the rear will be stiff and not allow proper compliance.

That would overwork the RR tire and cause a loose off, if not totally loose, condition. Running a RR spring that is too soft compared to the LR spring would have the opposite effect. The rear would want to roll over more so than the front and the car would be tight, or tight/loose off. There is an optimum spring split, RR softer, that will keep the car close to a balanced dynamic state and help the car on entry, through the middle and provide more bite off the corners.

Shock Installation – Because the front shocks were hitting the spring height adjuster, we needed to make a correction. We noticed that the stock hole where the top of the shock was anchored was positioned at the factory well towards the outside edge of the spring on both sides of the car.  With stock shocks and springs, this would work for clearance, but with our setup and equipment it was not.

The fix was to create a new “stock” hole farther inward and closer to the center of the spring. We reinforced this new hole by welding a washer on top of the frame. This provided a good bit of spacing between the spring spacer and the shock body.

To make sure we were good with the rules against using front weight jackers, we welded the height adjuster so it would not turn. This made it a spacer rather than a weight jacking device. We also installed a new set of gas pressure “stock” replacement shocks that were made for racing and more like what should be used on this type of car.

Tire Pressures and Sizes – I reviewed the existing tire sizes versus the tire pressures they had been running. The sizes were LF = 83.75, RF = 83.75, LR = 84.5 and RR = 85.0.  This only allowed a half inch of stagger in the rear, not nearly enough for this track. This too would facilitate a tight car.

The cold tire pressures they had been running were: LF = 17psi, RF = 23psi, LR = 15psi and RR = 14psi. The RF was high and the RR was low on pressures.  The fix was to try to change the tires around while re-pressuring the tires so that we could get front and rear stagger.

I traded the RF tire and the LR tires. This put a larger tire at the RF and a smaller tire on the LR.  We re-pressured the tires to: LF = 18psi, LR = 16psi, RF = 22psi and RR = 16psi.  With those pressures, we now had a front stagger of 1.00 inch and a rear stagger of 1.50 inches.

Weight Distribution – When we weighed the car before making any changes, the cross weight was at 53%.  After installing the new springs, changing the front caster and camber, moving tires around and adjusting tire pressures, we re-set the cross weight at 48.5%, or about 75 pounds of left rear weight.

With only 48.2% rear weight, the car did not need the 53% cross which represented 216 pounds of left rear weight. This was yet another reason why this car was way too tight. It was cross weight tight and was driving off the left rear tire under acceleration.

Another thing I noticed and corrected was the placement of lead in the rear of the car. The car builder had placed a considerable amount of lead well behind the rear end, on the rear hoop that protects the fuel cell. Although fairly common, this tends to create a cantilever effect and increases the polar moment. Polar moment is defined as a force trying to rotate or swing the rear end to the outside wall during cornering.

Some teams will experience a more neutral car by placing lead well behind the rear end, but this is more like a crutch for a tight car and although it helps the car into and through the turn, it will make the car loose off. It is much better to set up the car correctly and get the front to turn with a balanced spring setup and proper moment center and cambers. That way, you get into and through the turns better and still have more bite off.

It is always a good practice to keep all lead mounted inside the axles. We may decide later on to move it out, but for now we remounted the lead in front of the rear end and high in the car. A higher center of gravity is desirable on dirt cars for dry and slick tracks.

The Results – Once we got the springs installed, the tires mounted, the cambers set, the air pressures set and the ride heights and weight distributed like we wanted, we stood back and took a look at the car. It just looked better right away. I’ve seen lots of hobby stocks and this one looked like it was ready for the track.

The first chance we got to run the car, the driver noted that this car was now even better than his original Hobby Stock. The difference was that it turned better which allowed him to maneuver past guys that were hanging it out trying to point the car to get off the corners. And it had much more forward bite than before due to the more straight ahead attitude.

With his smooth and relentless style, this car was just what he wanted. If you prefer to sling the car in sideways, fight to get control and then hope for some semblance of bite off, then you might not want to copy us. Good luck and good racing.

Sources:

Afco Racing
www.afcoracing.com
800-632-2320

Allstar Performance
www.allstarperformance.com
269-463-8000

AR Bodies
www.arbodies.com
615-643-8827

Capital Motorsports Warehouse
www.cmwraceparts.com
800-278-2692

Five Star Bodies
www.fivestarbodies.com
262-877-2171

Harbor Freight
www.harborfreight.com
800-423-2567

Moser Engineering
www.moserengineering.com
260-726-6689

Optima Batteries
www.optimabatteries.com

QA1
www.qa1.net
800-721-7761

Quick Performance
www.quickperformance.com
515-232-0126

The post Fine Tuning the Stock Division appeared first on Hot Rod Network.

Have you ever wondered if all of the new technology is indeed moving us forward? Are our cars truly getting faster with the new setup trends? How would we ever know if all of the crazy setups we are seeing truly make the car faster and/or more consistent? The only way to know is to run an older, much older, setup against the others in head-to-head competition. And that’s exactly what we did.

I was fortunate enough to be allowed to work with one of the true legends of stock car racing and whose cars have won a disproportionate amount of races around the Southeast. Dick Anderson is, in short, old-school. The setups he normally runs are much stiffer than any others in this day and age. And, Dick runs a well-organized, well-equipped, and clean shop that was a pleasure to work in.

He recently decided to try going back to setups he ran with great success in the late ’70s and early ’80s just to see what would happen. The difference is in the stiffness of the front springs and sway bar. His cars are a big spring design and in our analysis we will translate spring rates from big spring to the equivalent in coil, using the same wheel rate, so you can compare to what this would mean for your car.

I will say up front that this was Dick’s idea, not mine. Most readers will assume because I have historically spoken out against running on coil-bind and bump rubbers that I might have influenced this process. I will admit that I was excited when Dick spoke of going in this direction, but I allowed this process to run its course and did not push an agenda of my own.

From the start, we knew we were going to learn something, even if it didn’t agree with our predictions. That’s what experimentation is all about. If you don’t go there, you never know. So we went and what follows is a true account of what we found. There were road bumps along the way, but all in all, we did make some discoveries that were backed by lap times and head-to-head comparisons.

A Review Of The Goals For Setups
As a preview to lead into this experiment, I want to go over what every race engineer on the planet will agree with as the basic concepts of goals for the optimum race car setup.

First and foremost, we want our car to be engineered so that all four tires will be loaded in the turns so the most traction can be attained, while at the same time providing a handling balance. This will allow the car to negotiate the turns more quickly. Speed gained at the slowest portion of the track will be carried all of the way around the track. So, our most significant performance gains are setup related.

Next, we want that speed to last a long time. In our case, we will need for the setup to provide a high level of traction and handling balance for 200 laps. What happens most of the time with many race teams is that they search for the fastest lap times and usually disregard consistency.

That in and of itself is a good goal, but it must be matched with a setup that will produce longevity of speed at the same time. So, once we find our fast lap time, we must compare that with how the speed drops off over a longer run.

A good balanced setup, where all four tires are working in unison, usually produces consistent lap times that don’t fall off nearly as much as less balanced setups. This has been my focus and the theme that has led me throughout my career. It’s the one message I constantly try to convey.

What I suspect, and Dick shares this opinion, is that most of the current setups are not balanced in the way I describe and will not have longevity of speed and handling over the course of a longer race. What we set out to do is prove or disprove that notion. Now, on to our test.

This year more than 40 teams showed up, coming from all over the country in some cases, to run one more race after their seasons had ended. It’s a 200-lap race, so endurance and consistency are important to success. In the end, the race was won by central Florida racer and veteran David Rogers.

Our first test session was conducted two weeks before the race and in attendance was Stephan Nasse who would eventually lead the most laps in the race. Nasse was consistently fast throughout the test, but couldn’t match our speed. We’ll get more into that later on.

The Car
Dick’s car that had been run all summer had recently been destroyed when the throttle stuck. Jeff Scofield was the driver and luckily he survived with just a few bruises and would pilot our test car. So, over that past month, Dick built a brand-new car of his own chassis design modeled after a Howe fourth-design front end that was in use around the early 1980s.

I measured the car and looked at the moment center locations and it was something we could work with. It (MC) was a little more left than I’m used to, but I felt that it would work in combination with the stiffer springs we were running. We decided on the spring rates and ran a computer simulation to derive the proper Panhard bar heights and rear spring split to go along with the high front spring rates in order to achieve a balanced setup.

We ended up with these springs: RF = 1,130; LF = 980; LR = 190; RR = 250 with a 1 1/8-inch diameter medium-rate sway bar with just one turn of pre-load. This would equate to a coilover car (based on our wheel rate translated to an equivalent coilover spring placement) with front spring rates of RF = 536 and LF = 485. Believe it or not, this is how stiff cars used to run. In the old days of the late ’70s and early ’80s, there were not so many coilover cars. Most cars were based on stock front clips and those used big springs.

When you think about how utterly stiff these springs are, stop to consider that when a car is on bumpstops or in coil-bind, the wheel rate goes to 1,500 to 2,000 ppi or more. So, in reality, we’re using about 1/3 the rate of the BBSS setups at mid-turn.

One other thing Dick wanted to try was using the small sway bar. We installed a 1 1/8-inch-diameter bar with medium thickness walls. He felt that we could put pre-load in this bar without making too much of a change in the crossweight that would affect the mid-turn handling. The sway bar can really help with bite off the corners, and Turn 4 at NSS is notoriously loose off.

We checked for Ackermann and reduced it to a minimum to gain about 1/32-inch of toe at mid-turn. We ran 1/8-inch of toe out. We also checked the rearend for square and the right rear tire patch alignment with the right front tire contact patch and both were perfectly aligned.

Dick ran a crossweight that I consider to be in the high range and it ended up at around 57.3, while his left side percent was 57.7. This matched up with his front-to-rear percent. All of the other settings such as the shocks, rear trailing arm angles, caster and cambers, and third link angle were what he had been running.

The Tests
Two weeks before the event, we tested at NSS. Initially we were fast right out of the trailer, but when pressed, entry and exit issues became apparent. We ran laps in the 17.70s to 17.80s range, which exceeded all other test cars by 0.2 to 0.3s. This was looking good, but we still had a way to go.

Turn entry was a problem and we couldn’t get the push out of the car. We made numerous changes that should have made the car loose as a goose, but didn’t. So, I made the conclusion that something mechanical was wrong. I learned that Dick had only 1/2-degree of right trailing arm angle in the car with almost 5 degrees of left trailing arm angle. This produced a lot of rear steer that made the car extremely tight.

Turn entry was a problem and we couldn’t get the push out of the car. We made numerous changes that should have made the car loose as a goose, but didn’t. So, I made the conclusion that something mechanical was wrong. I learned that Dick had only 1/2-degree of right trailing arm angle in the car with almost 5 degrees of left trailing arm angle. This produced a lot of rear steer that made the car extremely tight.

We put 2.5 degrees in the right arm and reduced the left arm to around 1 degree. That solved our tight problem. Then, as Jeff drove the car in deeper, it developed an entry push. He said it felt like the right front was falling over and the left rear was disconnected.

The 2 1/2 degrees of antidive at the RF was not enough to control the entry dive, so we boosted that up to 7 1/2 degrees of pivot angle, which is 3/4-inch of difference in bolt heights with the front higher. This is more than I’ve ever run, but when making changes, make one that is significant to determine if that is indeed a fix. It was.

By now we’d put about 40 laps on the tires and we were still in the 17.80s in lap times consistently. Still, the other cars there were turning high 17.90s and low 18.0s as the fastest laps and then falling off to the 18.20s after a few laps. We could run consistent 17.80s lap after lap. It was now time to put on stickers and make a run.

Our times not only didn’t improve on the initial sticker run, but the car’s handling went south too. Dick had experience with new sets of these tires that didn’t work, so we put the 50-60-lap first set back on and it was fine with the same lap times. So, we decided to put on another new set which turned out OK, but was slower and other issues cropped up.

At this point we were running, on the newer track tires, consistent 17.90s and 18.0s along with other fast cars that were testing. We felt good about things until strange issues began cropping up. It seemed as though every run presented a different problem. One run the car was tight, another it was loose. None of it made sense.

This issue continued on into the practice for the race and the race itself. Dick had made the decision to go back to his setup he had run all summer and one that had produced consistent wins over the past few years. Still, the car didn’t respond well and all in all it was a frustrating time for the entire crew.

Once he got back to the shop, he inspected everything and discovered that the rear differential in the car was coming apart. This problem was responsible for all of our handling problems. Unfortunately, we would not be able to prove our theory on the longevity, but we did demonstrate that competitive speed is possible with the stiffer setup.

Conclusion
This setup will be run again in the near future. Dick and I will test again with a new rearend. What most racers would have thought if presented with our plan beforehand is that it would surely be a half second, or more, slower than the setups that produce low and level attitudes of the front end.

How could a car go as fast as one where all of that aero downforce was being utilized? It’s simple, in the process of forcing and holding the front end down, and that is an accurate assessment of what is happening with the BBSS setups, the loading on the four tires becomes less optimal. There is good grip with the two front tires and with the right rear, but the left rear becomes less loaded and you end up with a car running on 3 1/2 tires.

If you reduce the traction on just one tire by half, the performance must suffer-and it does. What is especially true is that when you work with an unbalanced setup, the handling balance will change over the course of some number of laps and exactly when that happens is determined by how unbalanced the car is.

What we hope to eventually see is a re-evaluation of the setups used today and a return to sensible setups where the car is balanced dynamically and where the speed you gain carries on throughout the entire race. This is a track we will be on for some time, so keep watching for our results.

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