Handling Tips As Simple As ABC
The amount of misinformation regarding chassis set-up is staggering. These tips should help get you back on track.
Race car handling is the result of many complex relationships. Different aspects of your race car can cancel out any one or several of these handling tips. But for the most part, you can take these tips to the winner's circle.
A. (see illustration below) For short tracks, moving the Center of Gravity (CG) forward can make the car slow to respond when the steering wheel is first turned entering a corner.
On larger tracks where moderate acceleration occurs at the mid portion of the corner, having the CG too far forward will result in a larger wheel steering angle in the corner and typically a push (understeer) exiting the corner.
On short tracks where you have heavy acceleration, having a CG too far forward can result in rear wheel spin and a car that feels loose (oversteer) when trying to exit the corners.
B. The higher the CG is above the ground the more weight will transfer to the outside tires in a corner. A higher CG can also exaggerate the affects of Tip D below. Raising or lowering the CG can impact suspension geometry such as rear axle steer or camber gain in the front suspension.
C. Let the front roll center fall where it may in order for the front suspension to have good camber curves. Use the rear roll center to tune your race car's handling. Elevating the rear roll center tends to make the car looser (oversteer) in the mid portion of the corner when the centrifugal force is highest.
D. Many people refer to this parameter as roll couple distribution. No matter what you call it, increasing the Front % and decreasing the Rear % will tend to create a larger steering wheel angle and typically result in a mid turn push. There are no fixed numbers for this parameter. Your settings back at tip A will affect your ideal numbers.
E. Anybody can crank on the weight jacks until the race car has balanced handling. Cross weight preload is a way of measuring how efficiently the car is balanced. Ideally, the preload should be less than +/- 25 pounds. If the car is balanced and right front is greater than +25, then the car is telling you it wants a stiffer RF spring or a bigger sway bar. If the right rear is greater than +25, then you can likely benefit from a stiffer rear spring. After you make the spring change it will be necessary to readjust your corner weights.
F. Excessive split (left to right) can cause the car to lack high speed directional stability and/or be twitchy on heavy braking. With higher corner banking, increasing the LF & RR wheel rates will make the car turn too easy and often makes the car loose.
G. Typically for pavement tracks the front has a larger number. Dirt tracks typically require a larger number at the rear. In all cases, changes that decrease the rear number make the car tighter and increasing the rear number makes the car looser in the turns.