Suspension Setup
and tuning
Toe angle is the angle of the wheel to the
centerline of the vehicle as seen from above.
Neutral toe places the wheel parallel to the
centerline of the vehicle. For toe in, the front of
the wheel is closer to the centerline than is the
back of the wheel. In toe out, the front of the
wheel is farther away from the centerline than
the back of the wheel.
The toe setting affects the ability of a car to
drive and stop straight and to make precise
turns. Changes to these settings are made in
very small increments-about 1/8th of an inch
when measured at the tread of the tire. The
larger the change, the more pronounced the
handling characteristics (within limits of
adjustment).
A neutral toe car is the base case and the toe
setting options are as follows:
A car with front toe in will not turn as easily as a
neutral car, but, will be more stable when
accelerating or braking in a straight line.
A car with toe out will make turns more easily
than a neutral toe car, but, will have a tendency
to wander left or right under straight line
acceleration and braking.
The toe settings don't stay static, they change
when a car is moving. A front wheel drive car
will tend to push the wheels in or toe in. A rear
wheel drive car will toe out when driving. This is
one of the reasons that rear wheel drive cars
tend to handle turning and corners better than a
front wheel drive car. The settings when the car
is at rest must take into account what happens
when its moving.
Toe settings on the front wheels as viewed from above
the car.
Tuning the suspension, with the caster camber
and toe adjustments, is meant to make the car
easier to drive-particularly in turns. To
understand how a car behaves in a turn, we
need to make some observations.
When a car turns, the wheels are turned in the
direction of the intended turn. However, the
angle of the wheels and the angle that the car
turns don't always match. I know I know, it
sounds weird but its true.
When the wheels are angled more than the
angle that the car is turning, it is called
understeer. When the angle of the wheels are
less than the angle of the car turning, its called
oversteer.
The driver experiences understeer, as difficulty
making the turn, or needing to turn the wheel
more than it would seem necessary. Simply put
understeer is when a car is resisting making the
turn, preferring to go straight.
Oversteer is experienced as a car that turns too
easily, as if the steering wheel is too light or
sensitive to turning. A car with oversteer will
also feel as if the rear end is turning around
faster than the front of the car.
Understeer vs. Oversteer diagram