One of the most important and yet neglected factors influencing the
handling, and the fuel efficiency, of any car or truck is the wheel
alignment. Your vehicle’s ability to go, stop and change direction is
affected by the direction each of the wheels is pointing, and, whether
you drive a compact car or full-size SUV or pickup, the directional
control you get where the rubber meets the road is important for safety.
At
any given moment only a small patch of rubber, often smaller than the
palm of your hand, is supporting the weight of the vehicle and
transmitting all of the forces from the engine, brakes and steering to
the pavement. Proper wheel alignment helps ensure all of those forces
are going where they belong and the tires aren’t being overworked.
While
it may look to the naked eye like all of the tires are pointed straight
ahead, they are all at slight but important angles. There are three
different angles that affect wheel alignment: camber, caster and toe.
“Camber” is the degree to which a wheel departs from vertical (or
perpendicular with the road), as viewed from the front. The top of each
wheel is usually angled slightly inward. On an average car or truck, the
angle is usually less than a few degrees, and you need special
measuring equipment to determine the angle. The camber angle compensates
for the way tire rubber stretches and deforms when cornering, and helps
to make sure that the tire’s contact patch remains in full contact with
the road, including while going around corners.
“Toe” is the
degree to which a wheel departs from being parallel to the other wheel
on the same axle. If the front wheels (and the rears, if the vehicle has
independent rear suspension) are angled slightly towards each other (as
viewed from above) it’s called “toe-in.” “Toe-out” is when the wheels
are pointing slightly away from each other. This is to counter the
forces that push the wheels back into a more straight-ahead angle while
driving.
Finally, “caster” is the frontward or rearward angle
that the steering pivot point has from vertical, as considered from the
side. The forces from the caster angle are what give the steering wheel a
self-centering capability when you go down the road or relax your grip
after going around a corner.
Each of these can be adjusted with
links that are part of the suspension system. However, small variations
in the angles can have a big effect on how the car drives and on tire
wear. Sometimes hitting a big pothole or sliding into a curb can be
enough to affect the toe or camber angle by a single degree or less,
causing the vehicle to continuously pull in one direction or the other.
In
addition to causing the vehicle to pull in one direction or the other,
alignment problems also cause abnormally high, often uneven, tire wear.
This can lead to a blow-out that could cause an accident, excess
vibration that can be felt throughout the vehicle and reduced tire life.
Since
checking and adjusting wheel alignment requires precision equipment, it
should only be done by your dealer’s service department. You should
never attempt to adjust the alignment by hand at home. While most
service facilities offer both front-wheel-only alignment and four-wheel
alignment, it is usually best to go for four-wheel alignment.
On
rear-wheel drive cars and trucks with a solid rear axle, there usually
aren’t any adjustments available for the rear wheels. However, even in
this case, four-wheel alignment is important because the front wheels
will be adjusted relative to the rear wheels so that everything is
pointed in the right direction. Doing a front-only alignment can still
leave the car pulling in one direction or the other.
One way to
determine if your vehicle needs an alignment is to drive it down a
straight, flat road with little or no crown (the fall-off toward the
outer edge). The car should track straight ahead without you having to
tug on the steering wheel. If the vehicle diverges from straight ahead
without steering input, get it serviced soon.
You should also do a
regular visual inspection of all four tires for uneven wear. The tread
depth should be relatively consistent. You can quickly check the depth
using a penny stuck into the grooves. If the top part of Lincoln’s head
is covered by the rubber in each groove, you have enough tread left.
However, if the depth is significantly different on the inner or outer
edge of the tire, you could have an alignment problem that needs to be
corrected.
Most alignment work can be done quickly and often
doesn’t require any parts replacement unless the vehicle has hit
something severe and bent a suspension link. A proper alignment and a
regular tire rotation with each oil change will help your tires last
longer and make your vehicle safer and more enjoyable to drive.
This article is presented by Antelope Valley Ford Lincoln Mazda in Lancaster, California.
conventional tires. While checking the spare, don’t forget to take out the jack and make sure it’s working and all the parts are there. If your wheels have locking lug nuts, you wouldn’t want to get stranded with a flat tire that can’t be removed so make sure the key is in the car, as well. A first aid kit in the vehicle is always a good idea, too.