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B7. CASTER
Caster describes the forward/
backward angle of the front
steering block with respect
to a line perpendicular to the
ground. Caster angle affects
on- and off-power steering, as
it tilts the chassis more or less
depending on how much caster
is set. Generally, a lower caster
angle (more upright) is better on
slippery, inconsistent, and rough
surfaces, and a higher caster
angle (more inclined) is better on
smooth, high-traction surfaces.
Camber vs. Caster
Camber is all about contact patch - keeping as much tire on the ground as
possible. Camber and caster are related in that caster gives an amount of
EFFECTIVE CAMBER change when the front wheels are turned.
A higher caster angle (more inclined) has the effect of progressively leaning
the front tires into the direction of the corner as the wheels are turned. The
higher (more inclined) the caster angle, the greater the effective camber
change when the wheels are turned. This happens because the tops of the
wheels BOTH TILT towards the inside of the corner. With the proper amount
of caster this can increase steering, but if too much the tire only runs on the
inside edge and loses its contact patch and grip.
Compare that with static camber angle of the wheels, which is adjusted with
the car resting on a flat surface and the wheels pointed straight ahead. Static
camber adjustments primarily affect the outside wheels, since these are
the wheels that bear the majority of the load during cornering. The amount
of front static camber required to maintain maximum tire contact largely
depends on the amount of caster used. A higher caster angle (more inclined)
requires less static camber, while a lower caster angle (more upright)
requires more static camber. Check how the tires wear when you change
caster and re-adjust static camber if necessary until you get the desired (flat)
wear on the tire.
Another effect of caster is that it tilts the chassis when the front wheels are
turned. The higher the caster angle (more inclined), the more the inside
wheel lifts the inside of the chassis from the ground when the wheels are
turned into the corner. This tilts the chassis down to the outside, distributing
more weight to the outside rear wheel.
EFFECTS OF CASTER ADJUSTMENT
Lower Caster Angle (more upright)
• Decreases straight-line stability
• Increases steering at corner entry
• Decreases steering at mid-corner and corner exit
Higher Caster Angle (more inclined)
• Increases straight-line stability
• Decreases steering at corner entry
• Increases steering at mid-corner and corner exit
Note that depending on the track surface and tire hardness, these effects
may be different in that you may always have more steering with more
caster. This is especially true for high-traction tracks and/or soft tires.