Every racecar is built a little differently than another, even in the same class or division. The examples given are for a specific car (yes, these are real setups that have been used in real racing situations) and probably will not work exactly right for your racecar. We are trying to show tendencies for how to balance your setup and directions to go in making positive changes and why we are doing them. For setting up your car, apply the reasoning, not the specific changes or setups.
Setup information will include the four spring rates (LF, being the left front spring, shown in the left upper corner of the chart, RF in the right upper corner, LR in the left lower corner, and RR in the right lower corner). The front moment center is shown as height (off the ground)/width (from a centerline that is halfway between the two tire contact patches. A minus number represents a MC that is left of centerline). The Panhard bar is listed as left/right mounting heights off the ground in inches. The banking angle is shown in degrees and the last number shown is the g-force exerted on the car at mid-turn. Red is the starting setup, green the balanced setup.
This car would be very tight and would require a very low amount of cross weight percentage in order to make the car neutral. The two ends of the car are very different in what they desire to do-approximately 2.5 degrees difference in desired roll angle.
To balance this car, we could do several things:
1. Soften the front springs and reverse split the rates to: LR = 850, RF = 800 or softer.
2. Reduce the rear spring split to: LR = 185, RR = 175 for a leaf spring or Panhard bar car. For a metric four-link car with a high rear MC, the split needs to be around 50 pounds with the RR softer.
3. Raise the Panhard bar to 11/12. The metric car's MC is between 14.5 and 16.0 and not adjustable.
4. Redesign the front suspension points to move the dynamic width (after dive and roll) of the front MC to 2 inches left of centerline.
With these changes, the two suspension systems are now much closer to being balanced. The car will turn much better and we can use more cross weight percent that will load the LR tire and that will promote better bite off the corners.
As with the dirt stock clip car, this setup is a tight one. Because of the high g-forces encountered on asphalt, the front and rear roll angles are more than three degrees different resulting in a very unbalanced setup.
To balance this car, we could make these changes:
1. Change the front spring rates to: LR = 850, RF = 850.
2. Change the rear spring rates to: LR = 175, RR = 175.
3. Raise the Panhard bar to 11.5/12.5.
4. Move the dynamic MC to 3.0 inches in height and 4.0 inches right of centerline. This improves the camber change on the RF wheel and makes the front end more efficient to work harder to turn the car.
These changes will make both ends of this car perfectly balanced and the performance will be consistently fast because both ends are now working together.
With the low g-forces, small moment arm caused by the MC being located too far to the right of centerline and the stiff front springs, this car is both unbalanced and much too stiff for dirt racing. We can make changes similar to what we did to the stock clip Dirt Late Model, which are:
1. Soften and reverse split the front spring rates to: LR = 700, RF = 650.
2.Increase the rear spring split to: LR = 200, RR = 150.
3.Raise the Panhard bar to 10/11.
4.Move the dynamic MC width to (-) 2.0 inches left of centerline.