Tread Wear Indicators/Tire Wear Patterns; Tire Pressure For High Speed; Replacement Tires; Diagnosis And Testing Pressure Gauges - Jeep Cherokee 2000 Service Manual

XJ
DESCRIPTION AND OPERATION (Continued)
• 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-
cle.
Tire pressures have been chosen to provide safe
operation, vehicle stability, and a smooth ride. Tire
pressure should be checked cold once a month. The
spare tire pressure should be check at least twice
annually. Tire pressure decreases as the ambient
temperature drops. Check tire pressure frequently
when ambient temperature varies widely.
Inflation pressures specified on the placards are
cold inflation pressure. The vehicle must sit for at
least 3 hours to obtain the correct cold inflation pres-
sure reading. Or driven less than one mile after sit-
ting for 3 hours. Tire inflation pressures may
increase from 2 to 6 pounds per square inch (psi)
during operation, due to increased tire temperature.
WARNING: OVER OR 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).

TIRE NOISE OR VIBRATION

Radial-ply tires are sensitive to force impulses
caused by improper mounting, vibration, wheel
defects, or possibly tire imbalance.
To find out if tires are causing the noise or vibra-
tion, drive the vehicle over a smooth road at varying
TIRES AND WHEELS 22 - 3