WHAT IS A WHEEL ALIGNMENT ?
Wheel alignment
is important to the health of your car or truck. All of the elements
that make your car go straight are called "alignment".
If you
hit a big pothole, for example, it is possible to bump
alignment components out of their carefully
calculated locations, throwing out your balance and suspension.
Some
shops try to make it seem like rocket science, but wheel alignment
is a fairly straightforward affair. The inclusive term "wheel
alignment" involves three main measurements -- caster, camber,
and toe. These measurements have standards that a technician uses
as targets of adjustment.
In other words, get as close as you can to the right measurement.
The good news is that most modern cars only have adjustments for toe.
| Caster is
the tilting of the uppermost point of the steering axis either
forward or backward (when viewed from the side of the vehicle).
A backward tilt is positive (+) and a forward tilt is negative
(-). Caster influences directional control of the steering. When
the rear of the vehicle is lower than its designated trim height,
the front suspension moves to a more positive caster. If the
rear of the vehicle is higher than its designated trim height,
the front suspension moves to a less positive caster. With too
little positive caster, steering may be touchy at high speed
and wheel returnability may be diminished when coming out of
a turn. If one wheel has more positive caster than the other,
that wheel will pull toward the center of the vehicle. This condition
will cause the vehicle to pull or lead to the side with the least
amount of positive caster. |
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Camber is the tilting of the wheels from the vertical when
viewed from the front of the vehicle. When the wheels tilt outward
at the top, the camber is positive (+). When the wheel tilts
inward at the top, the camber is negative (-). The amount of
tilt is measured in degrees from the vertical. Camber settings
influence the directional control and the tire wear. Too much
positive camber will result in premature wear on the outside
of the tire and cause excessive wear on the suspension parts.
Too much negative camber will result in premature wear on the
inside of the tire and cause excessive wear on the suspension
parts. Unequal side-to-side camber of 1° or more will cause
the vehicle to pull or lead to the side with the most positive
camber. |
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Toe is a measurement of how much the front and/or rear wheels
are turned in or out from a straight-ahead position. When the
wheels are turned in, toe is positive (+). When the wheels are
turned out, toe is negative (-). The actual amount of toe is
normally only a fraction of a degree. The purpose of toe is to
ensure that the wheels roll parallel. Toe also serves to offset
the small deflections of the wheel support system that occur
when the vehicle is rolling forward. In other words, with the
vehicle standing still and the wheels set with toe-in, the wheels
tend to roll parallel on the road when the vehicle is moving.
Improper toe adjustment will cause premature tire wear and cause
steering instability. |
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