http://www.ncrscca.com/autocross-tuning-tips


Autocross Tuning Tips
Understeer
Vehicle is understeering but has sufficient body roll

Decrease front ride height.
Increase rear ride height.
Stiffen front dampers by two or three clicks.
Decrease front tire pressure by 2 PSI.
Increase camber degree (if possible).
Vehicle is understeering and has too little body roll, or is too stiff, or the brakes lock up quick

If the shock absorber is bottoming out, a stiffer spring is needed or the ride height needs to be increased.
If the shock absorber is not bottoming out, the user should change to softer front springs.
Soften the front dampers by two or three clicks.
Decrease tire pressure by 2 PSI.
Vehicle is understeering and has too much body roll

There is two reasons its understeering after the apex. One reason is, the front has too much roll and the other reason is pushing understeeing from rear.
Change to stiffer front springs.
Decrease front ride height and/or increase rear ride height.
Increase dampening force by two or three clicks or decrease rear dampening force by two or three clicks.
If the outside of the tire is worn, it should increase camber degree or change to a stiffer spring.
Vehicle is understeering after the apex

Front rebound dampening force is not enough make font dampers stiffer.
Or make pre-load equal to zero / add 3 to 5mm of pre-load.
Reduce front ride height by 3 to 5mm.
Rear spring is too soft add pre-load to rear or change to higher spring rate.
Vehicle is understeering before apex

Front springs or dampening force is too stiff change to softer front springs or use two or three click softer front setting. (Note: but these settings might decrease front response. In that case user may add 3 to 5mm or pre-load.)
Reduce front ride height by 3 to 5mm.
Add more camber to the front tires.
Add toe-out to rear tires.
Oversteer
Reason for oversteering
Rear inside load has decreased or there is not enough of it. If user cannot keep load on the rear tires (tires dont have grip) then the vehicle will slide. Rear ride height is too high when compared to the front.

Turn-in oversteering has too much roll

Rear roll speed is too fast, and there is insufficient rear compression damping force.
Change to stiffer rear springs.
Adjust rear damping force to two or three clicks stiffer.
Decrease rear ride height.
Turn-in oversteering is too stiff without enough rebound stroke

The rear tires start to slide before beginning to roll. Rear compression damping force is too stiff. Its like driving on ice.
Increase rear rebound stroke, decrease rear spring pre-load.
Change to softer rear spring rates.
Adjust rear damping by two or three clicks softer.
Decrease rear ride height.
Decrease tire pressure by 2 PSI.
After the apex oversteering

If the rear spring rate or damping force is too stiff, it begins to slide like on ice.
Adjust rear damping force to two or three clicks stiffer.
Decrease rear ride height.
Increase rear camber degree.
Before apex oversteering

Rear rebound stroke is not enough.
Adjust rear damping force to two or three clicks stiffer.
Need more traction

Needs more front rebound stroke
Adjust front damping force to two of three clicks stiffer.
Decrease front ride height.
Decrease tire pressure.
Brake lock (straight line braking before entering corner) Front is locked

Front spring rate is too stiff, front compression damping force is too stiff soften front dampers by two or three clicks or reduce spring pre-load.
Decrease front camber angle.
Pitching (excessive up and down movement) Front

Make sure there is sufficient amount of piston stroke.
If the damper is bottoming out, cut the bump rubber (must leave a minimum of 10mm), or change to stiffer spring rates, or raise up front ride height by 3 to 5mm.
If the damper is not bottoming out , make the front damping force stiffer by two or three clicks.
Rear

Rear rebound stroke is not enough, front compression damping force is too soft.
Adjust rear damping force by two or three clicks softer.
Decrease rear ride height by 3 to 5mm.
Decrease rear tire pressure only.