vehicle. They provide the best overall performance
for normal operation. The ride and handling charac-
teristics match the vehicle’s requirements. With
proper care they will give excellent reliability, trac-
tion, skid resistance, and tread life.

Driving habits have more effect on tire life than

any other factor. Careful drivers will obtain in most
cases, much greater mileage than severe use or care-
less drivers. A few of the driving habits which will
shorten the life of any tire are:

• Rapid acceleration

• Severe brake applications

• High speed driving

• Excessive speeds on turns

• Striking curbs and other obstacles
Radial-ply tires are more prone to irregular tread

wear. It is important to follow the tire rotation inter-
val shown in the section on Tire Rotation. This will
help to achieve a greater tread life.

TIRE IDENTIFICATION

Tire type, size, aspect ratio and speed rating are

encoded in the letters and numbers imprinted on the
side wall of the tire. Refer to the chart to decipher
the tire identification code (Fig. 1).

Performance tires have a speed rating letter after

the aspect ratio number. The speed rating is not
always printed on the tire sidewall. These ratings
are:

• Q up to 100 mph

• S up to 112 mph

• T up to 118 mph

• U up to 124 mph

• H up to 130 mph

• V up to 149 mph

• Z more than 149 mph (consult the tire manu-

facturer for the specific speed rating)

An All Season type tire will have either M + S, M

& S or M–S (indicating mud and snow traction)
imprinted on the side wall.

TIRE CHAINS

Tire snow chains may be used on certain models.

Refer to the Owner’s Manual for more information.

TIRES AND WHEELS

22 - 1

RADIAL-PLY TIRES

DESCRIPTION

Radial-ply tires improve handling, tread life and

ride quality, and decrease rolling resistance.

Radial-ply tires must always be used in sets of

four. Under no circumstances should they be used on
the front only. They may be mixed with temporary
spare tires when necessary. A maximum speed of 50
MPH is recommended while a temporary spare is in
use.

Radial-ply tires have the same load-carrying capac-

ity as other types of tires of the same size. They also
use the same recommended inflation pressures.

The use of oversized tires, either in the front or

rear of the vehicle, can cause vehicle drive train fail-
ure. This could also cause inaccurate wheel speed
signals when the vehicle is equipped with Anti-Lock
Brakes.

The use of tires from different manufactures on the

same vehicle is NOT recommended. The proper tire
pressure should be maintained on all four tires.

SPARE TIRE–TEMPORARY

DESCRIPTION

The temporary spare tire is designed for emer-

gency use only. The original tire should be repaired
or replaced at the first opportunity, then reinstalled.
Do not exceed speeds of 50 M. P. H. when using the
temporary spare tire. Refer to Owner’s Manual for
complete details.

TIRE INFLATION PRESSURES

DESCRIPTION

Under inflation will cause rapid shoulder wear, tire

flexing, and possible tire failure (Fig. 2).

Over inflation will cause rapid center wear and

loss of the tire’s ability to cushion shocks (Fig. 3).

Fig. 1 Tire Identification

Fig. 2 Under Inflation Wear

1 – THIN TIRE THREAD AREAS

Fig. 3 Over Inflation Wear

1 – THIN TIRE THREAD AREA

22 - 2

TIRES AND WHEELS

DESCRIPTION AND OPERATION (Continued)

Improper inflation can cause:
• Uneven wear patterns

• Reduced tread life

• Reduced fuel economy

• Unsatisfactory ride

• Vehicle drift
For proper tire pressure specification refer to the

Tire Inflation Pressure Chart provided with the vehi-
cles Owners Manual. A Certification Label on the
drivers side door pillar provides the minimum tire
and rim size for the vehicle. The label also list the
cold inflation pressure for these tires at full load
operation

Tire pressures have been chosen to provide safe

operation, vehicle stability, and a smooth ride. Tire
pressure should be checked cold once a month. Tire
pressure decreases as the ambient temperature
drops. Check tire pressure frequently when ambient
temperature varies widely.

Tire inflation pressures are cold inflation pressure.

The vehicle must sit for at least 3 hours to obtain the
correct cold inflation pressure reading. Or be driven
less than one mile after sitting for 3 hours. Tire
inflation pressures may increase from 2 to 6 pounds
per square inch (psi) during operation. Do not reduce
this normal pressure build-up.

WARNING: OVER

UNDER

INFLATED

TIRES

CAN AFFECT VEHICLE HANDLING AND TREAD
WEAR. THIS MAY CAUSE THE TIRE TO FAIL SUD-
DENLY, RESULTING IN LOSS OF VEHICLE CON-
TROL.

TIRE PRESSURE FOR HIGH SPEED

DESCRIPTION

Where speed limits allow the vehicle to be driven

at high speeds, correct tire inflation pressure is very
important. For speeds up to and including 120 km/h
(75 mph), tires must be inflated to the pressures
shown on the tire placard. For continuous speeds in
excess of 120 km/h (75 mph), tires must be inflated
to the maximum pressure specified on the tire side-
wall.

Vehicles loaded to the maximum capacity should

not be driven at continuous speeds above 75 mph
(120 km/h).

For emergency vehicles that are driven at speeds

over 90 mph (144 km/h), special high speed tires
must be used. Consult tire manufacturer for correct
inflation pressure recommendations.

REPLACEMENT TIRES

DESCRIPTION

The original equipment tires provide a proper bal-

ance of many characteristics such as:

• Ride

• Noise

• Handling

• Durability

• Tread life

• Traction

• Rolling resistance

• Speed capability
It is recommended that tires equivalent to the orig-

inal equipment tires be used when replacement is
needed.

Failure to use equivalent replacement tires may

adversely affect the safety and handling of the vehi-
cle.

The use of oversize tires may cause interference

with vehicle components. Under extremes of suspen-
sion and steering travel, interference with vehicle
components may cause tire damage.

WARNING: FAILURE TO EQUIP THE VEHICLE WITH
TIRES HAVING ADEQUATE SPEED CAPABILITY
CAN RESULT IN SUDDEN TIRE FAILURE.

DIAGNOSIS AND TESTING

PRESSURE GAUGES

A quality air pressure gauge is recommended to

check tire pressure. After checking the air pressure,
replace valve cap finger tight.

TREAD WEAR INDICATORS

Tread wear indicators are molded into the bottom

of the tread grooves. When tread depth is 1.6 mm
(1/16 in.), the tread wear indicators will appear as a
13 mm (1/2 in.) band (Fig. 4).

Tire replacement is necessary when indicators

appear in two or more grooves or if localized balding
occurs.

TIRE WEAR PATTERNS

Under inflation will cause wear on the shoulders of

tire. Over inflation will cause wear at the center of
tire.

Excessive camber causes the tire to run at an

angle to the road. One side of tread is then worn
more than the other (Fig. 5).

Excessive toe-in or toe-out causes wear on the

tread edges and a feathered effect across the tread
(Fig. 5).

TIRES AND WHEELS

22 - 3

DESCRIPTION AND OPERATION (Continued)

Content .. 150 151 152 153 ..