SERVICE PROCEDURES
TIRE INFLATION PRESSURES
WARNING: OVER
OR
UNDER
INFLATED
TIRES
CAN AFFECT VEHICLE HANDLING. THE TIRE CAN
FAIL SUDDENLY, RESULTING IN LOSS OF VEHICLE
CONTROL.
Under inflation causes rapid shoulder wear of the
tire tread and tire flexing. This can result in failure
of the tire. (Fig. 4).
Over inflation causes rapid center wear and loss of
the tire’s ability to cushion shocks (Fig. 5).
Improper inflation can cause:
• Uneven wear patterns
• Reduced tread life
• Reduced fuel economy
• Unsatisfactory ride
• The vehicle to drift.
Proper tire air inflation pressure specifications can
be found on the Vehicle Tire Placard provided with
the vehicle. See owner’s manual.
Tire pressures have been chosen to provide safe
operation, vehicle stability, and a smooth ride. Tire
pressure should be checked cold once per month.
Check tire pressure more frequently when the
weather temperature varies widely. Tire pressure will
decrease when the outdoor temperature drops.
Tire inflation pressures specified on the placard
are always cold inflation pressure. Cold inflation
pressure is obtained after the vehicle has not been
operated for at least 3 hours, or the vehicle is driven
less than one mile after being inoperative 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.
TIRE PRESSURE FOR HIGH SPEED
OPERATION
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.
TIRE AND WHEEL ROTATION
NON-DIRECTIONAL TREAD PATTERN TIRES
Tires on the front and rear axles operate at differ-
ent loads and perform different functions. For these
reasons, they wear at unequal rates, and tend to
develop irregular wear patterns. These effects can be
reduced by timely rotation of tires. The benefits of
rotation are especially worthwhile. Rotation will
increase tread life, help to maintain mud, snow, and
wet traction levels, and contribute to a smooth, quiet
ride.
Fig. 4 Under Inflation Wear
1 – THIN TIRE TREAD AREAS
Fig. 5 Over Inflation Wear
1 – THIN TIRE TREAD AREA
JX
TIRES AND WHEELS
22 - 5