what is caster and how does it affect handling on a car?

it is the relationship of the upper strut mount to the lower ball joint. zero caster is when the upper strut mount is directly above the lower ball joint when drawing a line connecting them. negative caster is when the upper strut mount is toward the front of the car. or ahead of the lower ball joint. positive caster is when the upper strut mount is toward the back of the car. or behind the lower ball joint.

the more positive the caster, the better stability in cornering and braking. the lower the caster, or towards negative, the more the car will understeer and dive when braking. hope that helps.

Positive caster offers more high speed stability, and an easier return to center after the turn (to a point). Too much negative caster will cause a car to "wander" and be really sensitive (at speed, but less predictable to input and the wheel will not return to center as easily. If there is a difference between sides the car will pull towards the most negative side.

go check out the ground control website they explain alot about it.

http://www.ground-control.com/gctalk5.htm