The way we approach the development of bite is related to how our car is setup, how the suspension systems are designed, and how the race track is shaped. In Part One of this two-part series, we learned something about how tires produce and keep traction. Now, we'll learn how to put that knowledge to practical use to develop more forward bite off the corners.
The way we develop bite for...
The way we develop bite for better acceleration off the corners has evolved over the years. What most teams used to do, even 5 years ago, is not what's being done today. Let's explore the many different ways we can help get more bite out of our race cars.
The Setup Helps
The way in which we set up the car can help us get more traction off the corners on flatter racetracks. One thing we did some years ago 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 LR spring is stiffer, then it will compress less than the RR spring and this will increase the amount of the total sprung weight supported by the RF and LR tires. This produces an increase in the crossweight percent, usually making the car tighter off the turns while under acceleration.
Now with the newer setups in both dirt and asphalt, we see more and more that teams are stiffening the RR spring rate. Bite suffers on the flatter tracks. It's useful to run the softest spring at the RR that will maintain the dynamic balance along with the stiffer front sway bars on asphalt cars. On dirt, we may reduce the amount of rear steer to compensate for the stiffer RR spring to get more bite.
When making changes to the spring rates, be sure to maintain a balanced setup. If you soften or stiffen the RR spring rate, the rear of the car will want to roll differently, creating an unbalanced setup. We must adjust the height of the rear Moment Center to compensate so the car will be balanced in the middle of the turns.
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 rearend.
The setup package in the car can have an affect 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.
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 and as power is applied, the rear tires suddenly lose all traction.
Many drivers will swear that 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.
The pullbar third link acts...
The pullbar third link acts much the same as the torque arm by extending under acceleration which serves to soften the application of torque to the rear wheels. The rotation of the rearend can be utilized to produce several effects such as introducing rear steer and increasing the crossweight percentage while under acceleration.
Spring and Shock Split Rates
For flatter tracks, the method of using rear spring split does not need to be substantial to accomplish the goal. On Asphalt Late Model cars, a 10- or 15-pound split (RR less than the LR) does what is needed. A 25-pound or greater split may be too much for a coilover 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 four-link suspension, a larger split is sometimes needed.
For the BBSS setups that are popular, but not necessarily needed, using less spring split (with the RR stiffer than the LR) helps provide bite and running even springs across the back is possible if you can raise the Panhard bar high enough to maintain a balance in the setup.