New Season Performance: Making A Slow Car Into A Fast Car

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.