To
understand caster you need to picture an imaginary
line that runs from through the upper ball joint and
extends through the lower ball joint. From the side
view the imaginary line will tilt forward or backward.
The tilting of this imaginary line is defined as
caster.
Caster is measured in degrees by using a caster
camber gauge. If the imaginary line described above
tilts towards the back of the car, at the top, then
you will have positive caster. If the imaginary line
tilts forward then you would have negative caster.
Positive caster provides the directional stability
in your racecar. Too much positive caster will make
the steering effort difficult. Power steering will
allow you to run more positive caster. Negative caster
requires less steering effort but can cause the car to
wander down the straightaway.
For oval track racing most racers run more positive
caster on the right side tire than on the left. The
caster split helps pull the car down into the turn,
helps the car turn in the center and helps it stay
hooked up on exit.
How much caster should you run? The amount and
split depends on the type of car and track conditions.
The details should be worked out with your car builder
and through testing.
