Question:How do I tell "normal" tire wear from
"abnormal" tire wear?
Answer:It's getting harder to tell because of changes
in tire and suspension designs. But as a rule, "normal"
wear is when the tread wears evenly across the entire surface of the tire.
The edges and center sections of the tread wear down at approximately
equal rates, and no bumpy, directional, feathered or cupped wear
patterns develop on the tread.
What's more, both front tires and both rear tires wear at
approximately the same rate. Front and rear tires usually wear
at different rates depending on which end is doing the driving.
The front tires on front-wheel drive cars and minivans, for example,
wear at a much faster rate than the rear tires. The rear tires
on rear-wheel drive performance cars or vehicles driven by someone
with a heavy foot also tend to wear out much faster than the ones
up front. But this is "normal" for the way in which
the vehicle is driven.
Heavy shoulder wear on the tires is also considered "normal"
if a vehicle is driven hard around corners. Rapid shoulder wear
on the front tires is also "normal" on some trucks and
minivans because of the steering geometry of the vehicle. The
front wheels are supposed to "toe out" with respect
to one another when they are turned to either side to compensate
for the different path the inside and outside wheels follow when
turning a corner. Some vehicles are better designed than others
to accomplish this. Those that aren't tend to produce more shoulder
wear than those that do. Rotating your tires frequently (every
8,000 miles or so) can help to equalize this kind of wear between
tires.
ABNORMAL WEAR
"Abnormal" tire wear is any type of wear that results
from a suspension or alignment problem, an internal tire fault,
or driving on underinflated or overinflated tires.
Abnormal wear would be where the inside or outside edge or
shoulder of the tire shows extreme wear, but the rest of the tread
shows little wear. This is called "camber" wear and
results from the tire leaning in or out (it should be straight
up and down when rolling down the road). Camber wear can be caused
by suspension misalignment, a bent strut, a mislocated strut tower
(often the result of unrepaired collision damage), a weak or broken
spring, a bent spindle, or collapsed or damaged control arm bushings.
The suspension should be inspected for worn or damaged parts,
and an alignment check performed to determine what needs to be
fixed to correct the problem.
If the tread develops a feathered or directional wear pattern
where the tread feels smooth when you run your hand across it
one way, but feels rough when you rub it in the opposite direction,
you have a "toe" wear problem. Toe refers to the parallelism
between the wheels as the roll down the road. If the wheels are
toed in or out with respect to one another, the tread will scuff
and develop a feathered wear pattern. This may be due to toe
misalignment, worn tie rod ends, worn idler arms, bent steering
linkage or bent steering arms. As with camber wear, the suspension
should be inspected, and the alignment checked to determine what's
causing the problem.
A "cupped" wear pattern on the tires can be caused
by a wheel and tire that are out of balance or by weak shock absorbers
or struts. This type of wear occurs because the wheel bounces
up and down as it rolls down the highway. The cure here is to
have the wheel balanced or replace the worn shocks or struts.
If the center of the tread is worn more than the shoulders,
it may be the result of overinflation. You're putting too much
air in your tires, causing them to bulge out in the center and
wear unevenly. Refer to the recommended inflation pressures in
your owner's manual or on the tire inflation decal in the glovebox
or door jamb.
If the shoulders of a tire are worn more than the center,
it may mean the tire doesn't have enough air in it. Underinflation
shifts the weight carried by the tire to the edges of the tread
causing the shoulders to wear more than the center. As with overinflation,
refer to the recommended inflation pressure for your vehicle.
NOTE: As mentioned earlier, heavy shoulder wear can also
be caused by hard driving, especially on winding or curving roads.
In this case, nothing abnormal is indicated, and the only correction
that's needed is a change in your driving habits.
Some low profile performance tires have a tendency to develop
what's called a "heel and toe" wear pattern if they
are not rotated every 5,000 to 8,000 miles. This is caused by
tread flex and the belt design of the tires. If tires with this
kind of wear tendency are not rotated, the tread may develop a
washboard wear pattern that causes annoying vibrations and/or
noise at speeds above about 40 mph. Once the wear pattern is
established, it may be too late to reverse it by rotating the
tires. Replacing the tires (and switching to a brand or design
that is less "quirky") may be the only way to cure this
kind of wear problem.
