Why Alignment Is Important
Alignment generally refers to the adjustment of a vehicle's front & rear
suspension parts. Proper alignment ensures that your vehicle handles correctly
& will help increase the life & performance of your tires.
When to Check Alignment
The alignment of your vehicle can be knocked out of adjustment from daily
impacts such as potholes & railroad crossings or by more severe accidents. You
should have the alignment checked if:
You know you have hit something.
You see a wear pattern developing on the shoulders of the tires.
You notice a difference in your vehicle's handling.
How Wheels Are Aligned
Alignment involves adjusting the angles of the wheels so that they are parallel
to each other & perpendicular to the ground. The three main adjustments made
in alignment are Camber, Caster, & Toe.
Camber is the angle of the wheel, in degrees, when viewed from the front of the
vehicle. Positive camber is when the top of the wheel is leaning out from the
center of the car. Negative camber is when the top of the wheel is leaning into
the car. If the wheel leans too far from the center, uneven wear will occur. The
camber angle is designed & adjusted per vehicle to keep the tires on the
outside of a curve flat on the ground during a turn. If you have too much
positive camber, your tires will wear on the outside. Too much negative camber
will wear them on the inside. If there is too much of a difference between the
camber settings on the front wheels, the vehicle will tend to pull sharply to
Caster is the forward or rearward tilt of the steering axis, measured from the
top of the tire as viewed from the side. The axis is formed by extending an
imaginary line through the upper & lower steering knuckles. The line extends
through the upper & lower ball joints on vehicles with front control arms, &
through the lower ball joint to the center of the strut mount on cars with
If the angle is towards the rear of the vehicle, the wheel has positive caster.
If the angle is too far to the front of the vehicle, the wheel has negative
Caster is set so that your car will tend to go straight ahead. Positive caster
has the effect of making your front wheels act as if your car was being pulled
from the front so that they will line up behind the point of pull, like a
child's pull toy.
Another example is the caster wheel found on furniture or on some shopping
carts. When you push a shopping cart equipped with caster wheels, it tends to
roll in a straight line because the wheels line up or trail behind the point of
pull. The greater the trail distance, the greater the tendency to roll straight
ahead. The caster setting on a vehicle is adjustable in order to increase or
decrease the effective trail distance.
Caster affects your vehicle's low-speed steering, high-speed stability as well
as how well your vehicle drives in a straight line (on-center feel). Too little
caster will cause your car to "wander" & make it feel unstable at high speeds.
Too much caster causes hard steering & can also result in excessive road shock
& shimmy. Caster does not affect tire wear.
Toe is the difference in the distance between the front of the tires & the
back of the tires. Usually, tires are set so that they are parallel with each
other. If the fronts of the tires are closer, the wheels are toe-in. If the
rears of the tires are closer, the wheels are toe-out.
Toe settings affect the handling characteristics of a vehicle in turns. Toe-in
introduces Understeer going into a curve & may make the vehicle feel like the
back end is trying to come around to the front end. Toe-out introduces Oversteer
in a curve & makes the vehicle feel like it is "diving" into the turn too
If the tires are toed-in too much, the tread will be "worn" off, starting from
the outside edges. If they are toed-out, the wear will start from the inside.
This type of wear is called "feathering" & can be felt by running your hands
across the tread of the tire.