Getting the car to stick is...
Getting the car to stick is a never-ending quest in every form of oval track racing.
Editor's Note: Second of a two-part series
The path to developing more traction while under power is related to our car's setup, suspension system design, and racetrack shape. Last month, we learned about how tires produce and keep traction. Now, we will learn how to put that knowledge to practical use to develop more forward bite off the corners.
The way in which we set up the car can help us get more traction off the corners on flatter racetracks. One step we can take is to split the rates of the rear springs so that the left rear spring is a higher rate than the right rear spring. When we accelerate, we transfer weight to the rear of the car. As that weight is applied, the rear springs must compress to absorb the added weight. If the left rear spring is stiffer, it will compress less than the right rear spring and this will increase the amount of the total sprung weight supported by the right front and left rear tires. This produces an increase in the crossweight percentage, usually making the car tighter off the turns while under acceleration.
When doing this, be sure to maintain a balanced setup. If you soften the right rear spring rate, the rear of the car will want to roll more, creating an unbalanced setup. We must raise the rear moment center to compensate so the car will not be overly tight in the middle of the turns.
The setup package in the car can have an effect on how the tires adapt to the application of power. Most of the time, if we can keep the car from being overly tight on entry and through the middle of the turns, we can avoid the all too common "tight/loose" condition that causes a car to be loose off the corners. A balanced setup helps to prevent this condition.
A torque arm is a device that...
A torque arm is a device that absorbs some of the engine torque when we open the throttle on exit off the corners. Various rates of springs and shocks can be used to adjust the resistance to rotation of the rear end.
As we have explained in the past, if a car is tight in the middle of the turns, we must add steering input to help increase the front traction to compensate. Then, as we pass mid-turn, the added steering generates more than enough front traction to overcome the tight condition and the car begins to get loose. All of this usually happens right about the time we start to get into the throttle. As power is applied, the rear tires suddenly lose all traction.
Many drivers will swear the car is loose. We need to learn to recognize this tight/loose condition so that proper adjustments can be made to the setup of the car for a more balanced mid-turn handling package. This condition is responsible for a major number of "loose off" problems.
For most applications, rear split does not need to be substantial to accomplish our goal. On asphalt Late Model cars, a 10- or 15-pound split does what is needed. A split of 25 pounds or greater may be too much for a coil-over car and cause an unbalanced setup that would be far too tight into and through the middle of the turns. For cars with big springs in the rear and a metric 4-link suspension, a larger split is sometimes needed.
To a lesser extent, splitting the compression rates of the rear shocks will accomplish a similar effect while the shocks are in motion and adjusting to the transfer of weight upon initial acceleration. This effect is very short lived, but can help reduce the shock to the tires that comes from the initial application of power. We would increase the compression rate in the left rear shock over the right rear shock to accomplish this effect.
We have learned that traction can be better maintained if we can decrease the amount of torque that reaches the rear tire contact patches at the initial application of power. Doing this helps the tires adjust to the transition of forces from lateral to longitudinal.