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In its
most basic form, a wheel alignment consists of adjusting the angles of the wheels so that they are perpendicular to the ground
and parallel to each other. The purpose of these adjustments is maximum tire life and a vehicle that tracks straight and true
when driving along a straight and level road.
If you know anything about wheel alignment, you've
probably heard the terms...
Camber, Caster and Toe-in.
Camber
 Camber is the angle of the
wheel, measured in degrees, when viewed from the front of the vehicle. If the top of the wheel is leaning out from the center
of the car, then the camber is positive ,if it's leaning in, then the camber is negative. If the camber is out of adjustment,
it will cause tire wear on one side of the tire's tread. If the camber is too far negative, for instance, then the tire will
wear on the inside of the tread.
 Camber
wear pattern
If the camber is different from side to side it can cause a
pulling problem. The vehicle will pull to the side with the more positive camber. On many front-wheel-drive vehicles, camber
is not adjustable. If the camber is out on these cars, it indicates that something is worn or bent, possibly from an accident
and must be repaired or replaced.
Caster
When you turn the steering wheel, the front wheels respond
by turning on a pivot attached to the suspension system. Caster is the angle of this steering pivot, measured in degrees,
when viewed from the side of the vehicle. If the top of the pivot is leaning toward the rear of the car, then the caster is
positive, if it is leaning toward the front, it is negative. If the caster is out of adjustment, it can cause problems in
straight line tracking. If the caster is different from side to side, the vehicle will pull to the side with the less positive
caster. If the caster is equal but too negative, the steering will be light and the vehicle will wander and be difficult to
keep in a straight line. If the caster is equal but too positive, the steering will be heavy and the steering wheel may kick
when you hit a bump. Caster has little affect on tire wear.
 The best way to visualize caster is to picture a shopping cart caster. The pivot of this type of caster,
while not at an angle, intersects the ground ahead of the wheel contact patch. When the wheel is behind the pivot at the point
where it contacts the ground, it is in positive caster. Picture yourself trying to push the cart and keep the wheel ahead
of the pivot. The wheel will continually try to turn from straight ahead. That is what happens when a car has the caster set
too far negative. Like camber, on many front-wheel-drive vehicles, caster is not adjustable. If the caster is out on these
cars, it indicates that something is worn or bent, possibly from an accident, and must be repaired or replaced.
Toe-in
 The toe measurement is the difference
in the distance between the front of the tires and the back of the tires. It is measured in fractions of an inch in the US
and is usually set close to zero which means that the wheels are parallel with each other. Toe-in means that the fronts of
the tires are closer to each other than the rears. Toe-out is just the opposite. An incorrect toe-in will cause rapid tire
wear to both tires equally. This type of tire wear is called a saw-tooth wear pattern as shown in this illustration.
If the sharp edges
of the tread sections are pointing to the center of the car, then there is too much toe-in.
If they are pointed to the outside of the car then there is too much toe-out. Toe is always adjustable on the front wheels
and on some cars, is also adjustable for the rear wheels.
Four Wheel Alignments
There are two main types of 4-wheel alignments.
In each case, the technician will place an instrument on all four wheels. In the first type the rear toe and tracking is checked,
but all adjustments are made at the front wheels. This is done on vehicles that do not have adjustments on the rear. The second
type is a full 4-wheel alignment where the adjustments are first made to true up the rear alignment, then the front is adjusted.
A full 4-wheel alignment will cost more than the other type because there is more work involved.
Other facts every driver should know about wheel
alignments.
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A wheel alignment should always start and end with
a test drive.
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The front end and steering linkage should be checked
for wear before performing an alignment.
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The tires should all be in good shape with even wear
patterns.
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Pulling problems are not always related to wheel
alignment, problems with tires, brakes and power steering can also be responsible. It is up to a good wheel alignment technician
to determine the cause.
Space Saving Spare Tire...
May Harbor Unpleasant Surprise
KA-BOOM! THUMP, THUMP, THUMP. Your car has a flat tire but there's no need
to worry. Those compact spares are much easier to maneuver than the old fashioned ones. In fifteen minutes you, or some good
Samaritan, are finished and back on the highway. But before reaching the next exit, pieces of your spare tire are flying over
the interstate.
A functional spare is a comforting accessory, but an underinflated or dry
rotted one is worthless. One that is buried under tons of trunk trash is useless, too. By avoiding the following pitfalls,
you can be assured that your baby tire is as capable as his big brothers.
UNDERINFLATION Underinflation
is the culprit in most bad spare scenarios. If your spare is low, it may shred on the way home or to the service facility.
The distance you can travel before this happens is directly related to the tire's inflation level. Check the pressure of the
spare, as well as the other four tires every month or two.
DRY ROTTING Tires, like
clothing, tend to deteriorate with age. Although this problem is not as common as underinflation, it bears consideration.
Tires do have a shelf life. After a period of time, they may begin to develop small cracks in the sidewall, your first clue
to this condition.
INACCESSIBILITY The leading
reason spare tires fall victim to underinflation and dry rotting is inaccessibility. If you do your own vehicle maintenance,
clear out the trunk and check that "Mickey Mouse" tire. If you take your car to a shop, most automotive technicians are happy
to check your spare if they can get to it. However, few will move your cargo for the sake of your spare.
FINAL NOTES 1) Some space
saving spares are made to travel up to 3,000 miles at highway speeds; most are limited to 50 m.p.h. It is, as car makers state,
for temporary use. Replace it with a full-size tire as soon as possible. 2) Keep your compact spare and its wheel together
and do not use them on another car. 3) Do not use tire chains on the space saving spare. They won't fit and will damage the
car as well as the chains. 4) Don't even think about driving through a car wash that pulls the car along guide rails. The
spare can get caught on the rail and damage the tire, wheel and possibly other parts of your car as well.
Remember: a flat tire in the trunk is about as useful
as a flashlight without batteries.
Scrap TiresWhen you buy a tire or battery you're likely
to pay a surcharge that goes to the Solid Waste Management Fund. It's part of the solution to the solid waste problems facing
our nation, a condition to which millions of junk tires annually make their contribution.
The good news is that used tires are a valuable resource; they just need
proper storage and handling. They can be used in asphalt paving, as a supplementary fuel in many industries and as a raw material
in molded plastic and rubber products.
The bad news: tens of thousands of tires land in the junk pile before their
normal life expectancy, says the Car Care Council. Due to motorists' poor maintenance habits, they're damaged and/or wear
unevenly, requiring replacement before their normal "retirement" time.
Storage of waste tires is a challenge to tire recyclers. In addition to
littering our landscapes they present a fire hazard and, because they provide a breeding place for insects and rodents, a
health hazard as well.
With periodic wheel alignment and balancing, along with monthly checks
of tire inflation, tires will last 10% - 20% longer, says the Car Care Council. That means fewer scrap tires to dispose of;
real savings to vehicle owners.
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