A "push-rod" trailing arm...
A "push-rod" trailing arm is designed to compress when the car is accelerating and this shortens the link, allowing the rear end to steer to the left, which tightens the car considerably. Most teams who find this useful always find it necessary to tighten the preload on the rubber biscuit to limit the amount of movement. Small amounts of rear steer go a long way towards tightening the car off the corner.
4. Front Wheel Camber Change - If the front of the car raises up as we get back into the throttle, it is possible this movement will cause the front wheels to change camber quickly and lose traction on initial application of power.
In a test session we were running at Concord Speedway in North Carolina a few years ago, the car was developing a slight push just as the driver was accelerating off the corner. We could see the front end raise up evidenced by the increase in the gap between the top of the left-front tire and the top of the wheelwell. We pulled the front shocks and increased the rebound rates in both front shocks. That solved the problem. Since we maintained the rebound split between the shocks, we determined that it was the sudden change in the camber off the front wheels that caused the front of the car to lose grip.
5.Rear Stagger - If we do not run a sufficient amount of rear stagger for the radius of the turns, especially where the car is initially accelerating, the rear end will drive the car to the right and towards the wall. I have known teams who had otherwise nicely balanced race cars that could not get off the turns without heading for the outside wall. The problem was insufficient rear stagger. In one case, the driver/owner was a former road racer who did not believe in "large" amounts of stagger. He used 1/2-inch of stagger when the track really wanted 1 3/4 inches. It took him over a year to wise up and then he started winning races.
We have talked about rear stagger and what the car wants at various types of racetracks. Use those guides and do not tune the cars handling with stagger. Give it what it wants and some of your exit problems will go away.
When attempting to tune your car's handling balance at the racetrack, always start with the middle phase of the turns. Run the car at a moderate speed through the middle well below race speed and note how far the steering wheel is turned. Speed up and do a few hot laps and again note the position of the steering wheel. If the wheel is turned farther at speed, the car is tight and if it is turned less, it is loose. If you have to steer to the right at mid-turn, bring the car back in! That simple test has helped many teams quickly determine the status of their setups so they will quickly know which direction to go in tuning the mid-turn handling.
Next, tune the entry balance and then last, tune the exit balance. When all three phases are balanced, work on driver finesse and practice passing maneuvers running high and low off the corners. With the car set up correctly, it is just a matter of experience and a little racing luck that brings that first win.
Radius to inside tire = 200 feet or 2400 inches (12" x 200')
Radius to outside tire = 2465 inches (2400 + 65" track width)
travels 2465 x 2 x Pi (3.1416) 2 = 7744 inches
Inside tire travels 2400 x 2 x Pi 2 = 7540 inches
Outside tire = 85 inches in circumference
Inside tire = 85 x (7540 7744) = 82.75
Correct Stagger = 85 minus 82.75 or 2 1/4 inches.
Multiply by 2 to achieve circle's diameter. Multiply that number by Pi (3.1416) to determine circumference. Divide total by 2 to reach half circle. You can get the same result by multiplying inches x Pi.
The rear stagger should be matched to the racetrack and not used to correct handling problems. A particular car at each racetrack will require a certain amount of rear stagger. The track radius used to determine stagger matters the most where the car will be accelerating. On some tracks, with cars using Detroit locker rear differentials, the accelerating portion radius will be larger than the mid-turn radius. Therefore, less stagger should be used so that both rear wheels are turning the same rpm off the corner to avoid wheel spin.