Front
End Vibrations and Alignment
by Austin Davis of TrustMyMechanic.com
Reader
Question:
My car shakes and vibrates on the freeway, does this
mean I need a front end alignment?
Dear
concerned car owner,
How
do you know if your car needs a front end alignment?
Vibrations, shimmy, and shaking felt in the steering
wheel are usually not a sign of needing a front end
alignment. A front end alignment, or four wheel alignment
as it is commonly referred to these days due to the
fact that the rear end of the vehicle can also be adjusted,
does just what the name implies align, or line up the
direction of the wheels so the vehicle is pointed in
a straight line.
Caster,
camber, and toe are terms used to describe the direction
of the wheel in relation to the body of the vehicle.
The front of the tire can be pointed in toward the center
of the vehicle thus "toed in." When the front
of the tire is pointed outward, it is referred to as
"toed out." Both of these problems can quickly
wear down the tread of a tire and can cause a "pull"
in one direction of the front end. The top of the wheel
can also lean in toward the center of the vehicle or
lean out away from the vehicle, causing a camber problem.
This situation can also cause tire wear and a pull to
one direction in the front end. Caster measures the
relationship of the left and right wheels to each other.
If one wheel is farther forward or back from the other
wheel, then there is a caster problem. Caster will usually
not cause a pull or tire wear, and this problem is commonly
found on wrecked vehicles.
So
what causes shimmy and shakes in the front end? The
biggest culprit is an out-of-balance or out-of-round
tire. As the tread on the tire wears, it will need to
be re-balanced to evenly distribute the weight of the
tire and the wheel. To do this, small lead weight is
attached to the outside of the wheel and a machine is
used to spin the tire and wheel to check balance. Tires
should be balanced and rotated every 12,000 miles (approximately
every four oil changes) to ensure even tire wear and
extend tread life. Out-of-round means the tire has worn
unevenly and cannot be balanced. An out-of-round tire
will have to be replaced. I have even seen new tires
that were out-of-round due to a manufacturing defect.
Hitting
a curb or large pot hole can cause the wheel weights
to come off, and sometimes the weights sling off the
wheel at high speed if they were not installed properly.
Out-of-round or out-of-balance will not cause a pull
in the front end, but will definitely cause shakes and
shimmies. If you can drive out of a shake or shimmy
by varying the speed of the car, it is a good clue that
you have an out-of-balance problem. A simple way to
check tire balance: if the shimmy is present at one
speed, but better or not present at a different speed,
then a balance problem is likely. An out-of-round tire
or a bent wheel will usually produce a wobble or shimmy
at all speeds, and replacement of the tire or wheel
is usually the cure.
Regular
tire rotation is the best way to extend the life of
a tire. Ask your mechanic which way to rotate the tires
depending on how the tread is wearing. Crossing tires
in an "X" pattern is usually the standard
way to rotate most tires, but moving the front tires
to the back in some cases is recommended to place the
best tires on the front. The majority of the stopping
power of the vehicle comes from the front brakes, so
the best tires should stay on the front for safety.
Caution: Some tires are "directional" and
must stay on one side of the vehicle, due to the fact
that the tire was made for the tread to only travel
in one direction.
A
vibration or shaking that is felt in the steering wheel
only when the brakes are applied is not a front end
alignment problem, but a brake problem. Have the brakes
inspected and make sure to tell your mechanic about
the shaking that you feel in the steering wheel when
you apply the brakes. This vibration may not be felt
by the mechanic on a quick test drive around the block,
so be specific. During this brake inspection, it would
also be a great time to rotate the tires since you are
already paying the labor to remove the wheels.
I
have developed a quick and easy to use maintenance schedule
that can help keep you up-to-date on the items mentioned
above. These schedules are free for you to view and
print out from our Website
Sincerely,
Austin
C Davis
