Of the thousands of components in a vehicle,
tires are probably the most important. Your
life literally depends on them one hundred
percent of the time you are on the road.
Recent events, in which tire failures have
allegedly caused a number of fatal crashes,
have focused attention on the vital role
tires play in vehicle safety. To separate
fact from hype, MSN Autos has gathered the
best information we could find on tires and
tire safety and condensed it into this handy
guide.
1. Check tire pressures and adjust at
least once a month.
According to studies conducted by the
National Highway Traffic Safety
Administration (NHTSA) on tire-related
crashes, the leading cause of tire failure
is underinflation.
Underinflation can have many causes,
including a gradual loss of pressure through
membranes in the tire itself. It is typical
for pressure to drop approximately 1 psi per
month and 1 psi for each 8-degree loss in
ambient temperature.
Underinflation has immediate effects on
vehicle handling (as well as fuel
consumption), but its potential impact on
overall safety and tire life are even
greater. It results in premature and uneven
tread wear on the outer edges.
Underinflation also increases stress on the
carcass itself, through flexing and
overheating, which can lead to structural
failures such as tread separation.
That's why it is imperative to check and
adjust tire pressure at least once a month
and before every long trip (over 250 miles).
Recommended pressures are printed on a label
located on the driver's doorframe or in the
glove box.
2. Inspect tires regularly for
abnormal wear or damage.
To ensure maximum tire life and safety,
give your tires a visual inspection at least
once a month and before long trips. This is
easily done at the same time you check
pressures.
Look for:
- Excessive or uneven tread wear,
which may indicate improper inflation or
steering and suspension misalignment;
- Cracks or bulges on the sidewalls or
tread;
- Chunking of the tread or any
indication of tread separation from the
carcass;
- Signs of puncture, or nails, screws,
glass, pieces of stone or any foreign
object imbedded in the tire.
If you detect any of these conditions,
take the vehicle in for further diagnosis
immediately. In most cases, punctures can be
repaired if their size is not excessive.
In general, external "plugs" are not
recommended. Repairs should be made from the
inside, and a complete inspection made while
the tire is off the rim. Sealing compounds
and other emergency aids should be treated
only as a means of moving the vehicle to a
safe location for repair.
If abnormal tire pressure loss occurs,
check the valve stems for leakage, as well
as the tire itself.
3. Rotate tires every 6,000 miles or
according to owner's manual.
Tire rotation is essential to achieve
even tread wear and maximum tread life. On
front-wheel-drive cars, for example, most of
the braking, steering and driving forces are
carried by the front tires, which inevitably
wear much faster.
A "cross-rotation pattern"—that is,
moving the left-front tire to the right-rear
axle, the right-front tire to the left-rear
axle, etc.—can best balance tread wear and
maximize tire life. That sequence can be
performed on any vehicle equipped with four
non-unidirectional tires. Designated by an
arrow on the sidewall, unidirectional tires
must be rotated only front to rear and rear
to front, on the same side of the vehicle,
so their direction of revolution does not
change.
All-wheel-drive and four-wheel-drive
vehicles are best suited to a lateral
rotation—left to right and right to left—at
the same end of the vehicle.
4. Maintain tires in proper balance.
Out-of-balance tires can not only cause
uneven tread wear and an uncomfortable ride
but also excessive wear on the suspension
and other components. An out-of-balance tire
can be detected by a severe thumping,
usually most pronounced at highway speeds.
If such a condition occurs, have your
tires dynamically balanced as soon as
possible. An experienced technician can
usually determine which tire is
out-of-balance by driving the car.
Tire balancing involves placing weights
in appropriate places on the bead or inner
circumference of the wheel. Tires should
always be balanced when first installed, and
whenever they are remounted.
5. Maintain steering and suspension in
proper alignment.
Misalignment of the steering and
suspension, either front or rear, can not
only adversely affect the steering feel and
stability of a vehicle, but also cause rapid
and uneven tire wear. If not corrected, this
misalignment can ruin a tire in a short time
and distance.
If you feel the steering "pulling" in one
direction or another when traveling straight
ahead on a flat road with no crosswind, or
if you notice uneven wear on the tires,
particularly front tires, you should have
the alignment checked and adjusted as soon
as possible.
Alignment should also be checked after a
vehicle has been involved in a collision or
if it is used continuously on rough roads,
particularly those with large potholes.
6. Never overload a tire.
Overloading is the second leading cause
of tire failure, next to underinflation.
All tires are designed to operate within
a maximum load range designated by a code on
the tire sidewall. Exceeding this can result
in both excessive wear and reduced tire life
due to structural damage, including the
potential for sudden failure.
In most vehicles, the maximum passenger
and cargo load for which the vehicle and
tires are designed is printed on the same
label that designates recommended tire
pressures. That load, particularly in the
case of trucks and SUVs, may be
substantially less than the vehicle is
physically able to contain. It is
critical that the maximum allowable load
never be exceeded.
When determining the actual load in your
vehicle, don't overlook the tongue-weight of
a trailer if you are trailer towing, since
it also acts directly on the vehicle's
tires.
7. Avoid overheating tires.
Heat, like load, is the enemy of tire
life. The higher the heat it is subjected
to, the shorter the tire's life—in terms of
both tread wear and structural resistance.
High speeds, high loads, underinflation,
coarse pavement or concrete, and aggressive
driving, including high cornering loads and
hard braking, all contribute to high tire
temperatures. Combined with high ambient
temperatures and continuous use, they can
create extreme circumstances and cause
sudden tire failure.
To maximize tire life and safety,
therefore, it is important to minimize the
simultaneous occurrence of such conditions.
Be particularly vigilant at high
temperatures and adjust your driving style
to consider its effect on tire life and
performance.
8. Replace tires when required.
Your vehicle's tires should be replaced
if:
- Any portion of the tread is worn to
the "wear indicator bars"—lateral bars
molded into the tire grooves at about 20
percent of their new tread depth—or to a
depth, as measured in a groove, of
1/16th inch or less.
- Tread wear is severely uneven (in
which case have the wheel alignment
checked) or the center is worn much more
than the edges (be more vigilant about
tire pressures).
- The tire sidewalls are severely
cracked or there are bulges anywhere on
the tire.
- There is any indication of tread
separation from the tire carcass.
- The tire has been punctured and
cannot be satisfactorily repaired.
There are other reasons you may need new
tires, as well. If you have been running on
winter tires, then a change is in order in
the spring. Using snow tires on dry roads
accelerates their wear significantly and
diminishes both traction and handling
ability.
9. Install tires in matched pairs or
complete sets.
Installing different tires on the left
and right sides can significantly upset the
handling balance of a vehicle—not to mention
its ABS operation. For that reason, it is
imperative that tires be installed in front
or rear pairs, or complete sets.
Those pairs should be the same
construction, size, brand and type, with
approximately the same tread wear. In most
cases, if you have to buy one new tire, you
should buy a pair. It is essential that
side-to-side pairs be the same and highly
desirable that front and rear pairs also be
matched, except in cases such as
high-performance cars with larger tires in
the rear.
If you replace only two, the new tires
should generally go on the rear wheels,
regardless of whether the vehicle is FWD,
RWD, or AWD. It is important to maintain
maximum traction at the rear wheels to
ensure stability. Putting new tires on the
front and nearly worn-out tires on the rear
wheels of any vehicle is a recipe for
instability. It is thus very important to
avoid dramatic differences in tread wear,
front-to-rear.
Under no circumstances should you have
tires of different construction (radial and
bias ply) or different classification
(all-season and winter) on opposite ends or
sides, since handling can be adversely
affected.
10. Select the right tires for your
vehicle and driving environment.
Recent improvements in "all-season" tires
have substantially advanced the concept of
one-tire-for-all-needs. On the other hand,
more specialized tires than ever are now
available for high performance, rain, snow,
ice, off-road and touring. Some are even uni-directional,
"run-flat" and even "green."
Most drivers are happy just to know they
have "all-season" tires, and that is the way
most new vehicles are equipped. These are a
benign compromise, sacrificing exceptional
capability in any one area of performance
for acceptable capability in all.
Within that premise, however, there are
huge variations in actual performance.
Unfortunately, factors that improve one tire
characteristic tend to diminish another. For
example:
- A hard tread compound may enhance
tread life and fuel economy but detract
from both wet and dry traction;
- Short, stiff sidewall construction
may enhance cornering power and
directional stability but detract from
ride quality;
- A wide tread with minimal grooving
may enhance dry grip but detract from
traction in wet and snowy conditions;
- An aggressive, open tread may
enhance snow traction but aggravate tire
noise and sacrifice tread life on
pavement.
In addition to dry asphalt, tires may be
expected to function on mud, snow, ice, sand
or gravel, in temperatures from above 140°F
to below -40°F. You get some idea of the
multiple tradeoffs designers have to make.
Just consider that exceptional virtues
are probably achieved at the expense of
others. Determine what your primary needs
are, and narrow your choices accordingly.
Then, if possible, drive a similar vehicle
equipped with the tires you are considering.
Canadian auto journalist Gerry Malloy
is a regular contributor to Sympatico / MSN
Autos Canada.
