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WARNING!Overloading of your tires is dangerous. Overloading
can cause tire failure, affect vehicle handling, and
increase your stopping distance. Use tires of the
recommended load capacity for your vehicle. Never
overload them.
TIRES — GENERAL INFORMATION
Tire Pressure
Proper tire inflation pressure is essential to the safe and
satisfactory operation of your vehicle. Three primary
areas are affected by improper tire pressure: Safety
WARNING!• Improperly inflated tires are dangerous and can
cause accidents.
• Under-inflation increases tire flexing and can re-
sult in tire failure.
• Over-inflation reduces a tire’s ability to cushion
shock. Objects on the road and chuckholes can
cause damage that result in tire failure.
• Unequal tire pressures can cause steering prob-
lems. You could lose control of your vehicle.
• Over-inflated or under-inflated tires can affect
vehicle handling and can fail suddenly, resulting
in loss of vehicle control.
• Unequal tire pressures from one side of the ve-
hicle to the other can cause the vehicle to drift to
the right or left.
(Continued)304 STARTING AND OPERATING
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WARNING! (Continued)• Always drive with each tire inflated to the recom-
mended cold tire inflation pressure.
Economy
Improper inflation pressures can cause uneven wear
patterns to develop across the tire tread. These abnormal
wear patterns will reduce tread life resulting in a need for
earlier tire replacement. Under-inflation also increases tire
rolling resistance and results in higher fuel consumption.
Ride Comfort and Vehicle Stability
Proper tire inflation contributes to a comfortable ride.
Over-inflation produces a jarring and uncomfortable
ride.
Tire Inflation Pressures
The proper cold tire inflation pressure is listed on the
driver’s side “B” Pillar. Some vehicles may have Supplemental Tire Pressure
Information for vehicle loads that are less than the
maximum loaded vehicle condition. These pressure con-
ditions will be found in the “Supplemental Tire Pressure
Information” section of this manual.
The pressure should be checked and adjusted as well as
inspecting for signs of tire wear or visible damage at least
once a month. Use a good quality pocket-type gauge to
check tire pressure. Do not make a visual judgement
when determining proper inflation. Radial tires may look
properly inflated even when they are under-inflated.
CAUTION!After inspecting or adjusting the tire pressure, al-
ways reinstall the valve stem cap. This will prevent
moisture and dirt from entering the valve stem,
which could damage the valve stem.
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Inflation pressures specified on the placard are always
“cold tire inflation pressure.” Cold tire inflation pressure
is defined as the tire pressure after the vehicle has not
been driven for at least three hours, or driven less than
1 mile (1.6 km) after a three hour period. The cold tire
inflation pressure must not exceed the maximum infla-
tion pressure molded into the tire sidewall.
Check tire pressures more often if subject to a wide range
of outdoor temperatures, as tire pressures vary with
temperature changes.
Tire pressures change by approximately 1 psi (7 kPa) per
12°F (7°C) of air temperature change. Keep this in mind
when checking tire pressure inside a garage, especially in
the winter.
Example: If garage temperature = 68°F (20°C) and the
outside temperature = 32°F (0°C) then the cold tire inflation pressure should be increased by 3 psi (21 kPa),
which equals 1 psi (7 kPa) for every 12°F (7°C) for this
outside temperature condition.
Tire pressure may increase from 2 to 6 psi (13 to 40 kPa)
during operation. DO NOT reduce this normal pressure
build up or your tire pressure will be too low.
Tire Inflation Pressure – 4500/5500 with Steel
Carcass Ply Tires
This type of tire utilizes steel cords in the sidewall. As
such, they cannot be treated like normal light truck tires.
Adjusting tire pressure must be performed by personnel
trained, supervised and equipped accordingly.
Inflation Pressure Adjustment When Mounted to
Vehicle
During procedures when adding tire inflation pressure,
the technician or individual must utilize a remote infla-
tion device, and ensure that all persons are clear of the
trajectory area.306 STARTING AND OPERATING
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4500/5500 Tire Inflation
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When adjusting inflation pressure to a tire and wheel
assembly mounted on a vehicle, use a Remote Mount
Automatic Inflation Kit or see your authorized dealer.
NOTE: Never attempt to re-inflate a tire and wheel
assembly which has been run flat or is extremely under-
inflated without first removing the tire from the wheel
assembly for inspection.
Personnel trained, supervised, and equipped according
to Federal Occupational Safety and Health Administra-
tion (OSHA) should perform this work.
Inflation Pressure Adjustment When Not Mounted to
Vehicle
When adjusting inflation pressure to a tire and wheel
assembly not mounted on a vehicle, use a Remote Mount
Automatic Inflation Kit and a Tire Inflation Cage or see
your authorized dealer. Tire Pressures for High Speed Operation
The manufacturer advocates driving at safe speeds
within posted speed limits. Where speed limits or condi-
tions are such that the vehicle can be driven at high
speeds, maintaining correct tire inflation pressure is very
important. Increased tire pressure and reduced vehicle
loading may be required for high-speed vehicle opera-
tion. Refer to original equipment or an authorized tire
dealer for recommended safe operating speeds, loading
and cold tire inflation pressures.
WARNING!High speed driving with your vehicle under maxi-
mum load is dangerous. The added strain on your
tires could cause them to fail. You could have a
serious accident resulting in serious injury or death.
Don’t drive a vehicle loaded to the maximum capac-
ity at continuous speeds above 75 mph (120 km/h).308 STARTING AND OPERATING
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Radial Ply Tires
WARNING!Combining radial ply tires with other types of tires
on your vehicle will cause your vehicle to handle
poorly. The instability could cause an accident result-
ing in serious injury or death. Always use radial ply
tires in sets of four (or six, in case of trucks with dual
rear wheels). Never combine them with other types
of tires.
Cuts and punctures in radial tires are repairable only in
the tread area because of sidewall flexing. Consult your
authorized tire dealer for radial tire repairs. Tire Spinning
When stuck in mud, sand, snow, or ice conditions, do not
spin your vehicle’s wheels faster than 30 mph (48 km/h)
or for longer than 30 seconds continuously without
stopping when you are stuck.
Refer to “Freeing A Stuck Vehicle” in “What To Do In
Emergencies” for further information.
WARNING!Fast spinning tires can be dangerous. Forces gener-
ated by excessive wheel speeds may cause tire dam-
age or failure. A tire could explode and injure some-
one. Do not spin your vehicle’s wheels faster than
30 mph (48 km/h) or for more than 30 seconds
continuously when you are stuck, and don’t let
anyone near a spinning wheel, no matter what the
speed.
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Tread Wear Indicators
Tread wear indicators are in the original equipment tires
to help you in determining when your tires should be
replaced. These indicators are molded into the bottom of the tread
grooves. They will appear as bands when the tread depth
becomes 1/16 in (2 mm). When the tread is worn to the
tread wear indicators, the tire should be replaced.
Many states have laws requiring tire replacement at this
point.
Life of Tire
The service life of a tire is dependent upon varying
factors including, but not limited to:
• Driving style
• Tire pressure
• Distance driven1 — Worn Tire
2 — New Tire310 STARTING AND OPERATING
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WARNING!Tires and spare tire should be replaced after six years,
regardless of the remaining tread. Failure to follow
this warning can result in sudden tire failure. You
could lose control and have an accident resulting in
serious injury or death.
Keep dismounted tires in a cool, dry place with as little
exposure to light as possible. Protect tires from contact
with oil, grease, and gasoline. Replacement Tires
The tires on your new vehicle provide a balance of many
characteristics. They should be inspected regularly for
wear and correct cold tire inflation pressure. The manu-
facturer strongly recommends that you use tires equiva-
lent to the originals in size, quality and performance
when replacement is needed (refer to the paragraph on
“Tread Wear Indicators”). Refer to the Tire and Loading
Information placard for the size designation of your tire.
The service description and load identification will be
found on the original equipment tire. Failure to use
equivalent replacement tires may adversely affect the
safety, handling, and ride of your vehicle. We recommend
that you contact your original equipment or an autho-
rized tire dealer with any questions you may have on tire
specifications or capability.
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