Stay out of the trajectory (1) as indicated in the illustration.
WARNING:Do not mount tube type tires on tubeless wheels or
tubeless tires on tube type wheels. To do so could result in tire
or wheel failure and cause property damage, personal injury or death.
Preserving proper inflation pressure is a very important maintenance
practice to make sure safe vehicle operation and long life for the tires.
Failure to maintain correct inflation pressure may result in sudden tire
destruction, improper vehicle handling, and may cause rapid and
irregular tire wear. Therefore, inflation pressures should be checked daily
and always before long distance trips.
Follow the tire manufacturer’s recommended cold inflation pressure for
the tire size, type, load range (ply rating) and axle loading typical for
your operation. (Each steer axle tire load equals
1 2steer axle loading;
each drive tire load is1 4the axle loading if fitted with four tires).
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Checking Tire Pressure
Always check inflation pressure when tires are cold. Never bleed air from
hot tires to relieve normal pressure build-up. Normal increase in pressure
due to service conditions is 10–15 psi (69–103 kPa), which is allowable
in truck tires.
Tires should be properly inflated to manufacturers’ recommended
pressure for the size and service load in which the vehicle is being used.
See the specific tire manufacturer with which your vehicle is equipped
with for the latest information concerning service load and inflation
pressure.
It is particularly important to keep moisture from the inside of tires, and
proper selection of air compressor equipment, proper air line routing,
and the use of shop air dryers is strongly recommended to avoid
moisture in the high pressure air used for tire inflation.
Under-inflation
Tires should not be permitted to become under-inflated. Increased
flexing due to under-inflation causes heat build-up within the tire
components. This leads to reduced strength, breakdown of the rubber
compounds, and possible separation of the tire components (i.e., ply and
tread separation and reduced retreadability).
Under-inflation is the primary cause of premature tire concerns including
sudden loss of air. In addition, low inflation causes an increase in rolling
resistance. This results in reduced fuel mileage, a loss in tread mileage,
and uneven wear due to increased tread movement. To determine proper
inflation, see the tire manufacturer load and inflation guide which can be
found on the tire manufacturer website or at your local truck tire dealer.
Tire Inspection
Check the tires for abnormal wear patterns and proper inflation
pressures. Cut or broken tire casings must be repaired or replaced.
Tires should also be inspected for the following conditions. If any are
present, the tire should be removed and repaired, retreaded or scrapped
as the condition indicates.
•Any blister, bump or raised portion anywhere on the surface of the
tire tread or sidewall (other than a bump made by a repair). These
indicate the start of internal separation.
•Any cut that reaches to the belt or ply cords, or any cut that is large
enough to grow in size and depth.
•Any nail or puncturing object.
•If any stone or object is held by a tread groove and is starting to drill
into the tread base, remove the object.
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Proper tire inflation, toe-in adjustment, loads, and road speeds are
important factors governing tire mileage, steering ease and
maneuverability.
Tire Loading
WARNING:Loading tires beyond their rated capacity decreases
tire life requiring more frequent replacement of tires. Overloading
creates an unsafe condition that may result in sudden air loss from a
tire failure resulting in an accident that could cause property damage,
personal injury or death.
Note:Your GAW/GVW rating is correct at the time of your vehicle
production, and reflects the exact rating of the tires specified. When
replacing tires, make sure that the replacement tire load rating (listed in
pounds and kilograms on the tire sidewall) is the same or higher than
the tire that is removed. Failure to do so adversely affects maximum load
carrying capacity. Tires with the same size specification do not always
have the same load specification.
Matching Tires
Dual Tires:Dual tires should be matched using tires of equivalent size.
Tires which differ more than
1 4inch (6 millimeters) in diameter or3 4inch (19 millimeters) in circumference should not be mounted on the
same dual wheel assembly.
Mixing:Never mix bias and radial tires on this vehicle. Never mix
different tire sizes or constructions on the same axle.
Rotation:
Rotation is always advisable:
•If front (steering) axle tires become irregularly worn, move to rear
position.
•In a dual assembly, reverse the position of the tires if one tire wears
much faster than its mate.
•On the drive axle, if heel and toe wear or alternate lug wear occurs,
rotating the tires from one end of the axle to the other end of the
axle may help even out this wear.
Rotation may not advisable:
•Front (Steering) Axle:Tires must be removed when tread is worn
to 4/32 inch (3 millimeters) or less. Retread or rotate worn tires to
drive position. Retreaded tires are not recommended to be used on
steering axles.
•Rear Axles:Tires must be removed when tread is worn to 2/32 inch
(2 millimeters).
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If rib tire is used on front axle and lug or off-road type on rear axle
positions:
•Front (Steering) Axle:Replace tires at front wheels when tread is
worn to 4/32 inch (3 millimeters) or less.
•Rear Axles:Tires must be removed when the tread is worn to
2/32 inch (2 millimeters) or less. Tires identified with the word
re-groovable molded on the sidewall can be re-grooved. A minimum
of 3/32 inch (2.5 millimeters) of under-tread must be left at the
bottom of the grooves.
Wheel and Tire Balancing
Out-of-round or out-of-balance wheels or tires can cause vehicle
vibration, bounce and shimmy. Replace damaged or out-of-round wheels.
Out-of-round tires and wheel assemblies can be corrected by re-clocking
the tire relative to the wheel.
The tire and wheel assembly should then be dynamically balanced.
Tire Wear
Radial tires can exhibit three types of normal wear patterns:
•Even
•Erosion
•Chamfer
Even wear:A sign that the tire is being properly used and maintained.
Erosion wear:Also called rolling wear, channel or river wear. Erosion
wear is found more often on free-rolling tires. This is an indication that
the tire is being used in a slow wearing operation. What happens is that
the belt plies are held very rigid and the tread is not allowed to distort
as it passes through the contact area. Wear only occurs at the edge of
the tread. No corrective action required. If erosion gets to be 1/16 inch
(2 millimeters) or more, the tire may be rotated to a drive axle.
Chamfer or shoulder wear:With tires inflated properly, this is a
normal tendency of most radial tire designs. If both inside and outside
shoulders are wearing evenly around the tire, no further action is
required. Over-inflation is not effective in correcting this effect.
Irregular Wear:If irregular wear is present, check the axle alignment,
tire pressure, wheel balancing, shock and suspension component
condition, and wheel bearing end play.
This condition not only shortens tire life, but adversely affects the
handling of your vehicle, which is dangerous.
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Rotating tires from one wheel position to another is a way often used to
even out many types of irregular wear or to avoid it altogether. Some of
the more effective tire rotation programs are:
•Steer tires that have developed some type of irregular wear pattern
can be rotated to drive axles if rib tires are being used on all wheel
positions. Applying steer tires to a drive position often cleans them
and they can be moved back to the steer axles or run out to re-tread
stage on the rear axle.
•Another rotation possibility for fleets with rib tires in all wheel
positions is to break in the new steer tires in the drive axle positions,
then move them to steer axles. This wears away tread rubber
relatively quickly in the early life of a tire when it is most likely to
develop an unusual wear pattern.
•Drive axle tires may be placed on the other end of the same axle so
that direction of rotation is reversed. This is often helpful if a heel
and toe or alternate lug wear pattern has developed.
Irregular wear can be minimized by:
•Using the right inflation pressure for the load being carried.
•Maintaining proper front wheel alignment, especially toe-in, to
specifications.
•Maintaining proper tire and wheel balance.
•Maintaining shock absorbers and suspension components.
Use of Tire Chains
See the chain manufacturer’s recommendation for correct tire chain
usage, installation and removal.
WHEELS
General Information
Note:Remember to replace the wheel air valves when the road tires are
replaced at the end of their useful lives.
Wheel bearings should be inspected, lubricated and adjusted at regular
intervals. This is especially important if operating in deep sand, mud or
water. See theCapacities and Specificationschapter.
Mount wheel balance weights on the dome-side of the wheel only. Failure
to do so may result in loss of wheel weight or damage to brakes or
wheels.
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Oil-lubricated Front Wheel Bearings
During normal vehicle duty cycle, the lubricant and air inside the
hub/wheel cavity expands and, if not vented, causes pressure build-up
that could cause accelerated seal wear. There are two venting methods
that can be used to prevent pressure build-up:
•a slit or small hole in the rubber check vent
•the window.
Over a period of time, if not routinely cleaned, a slight film of oil can
collect dirt around the rubber fill plug and face, which could appear to
be a leak. Routine cleaning makes sure that the lubricant level can be
easily observed through the window as intended. In situations where the
window is clean on the outside but discolored on the inside, the
lubricant level may be checked by inserting a finger through the rubber
check vent hole.
The specified lubricant level for a window-type hubcap is from the
minimum line to 5/16 inch (8 millimeters) above the minimum line. If the
lubricant level should suddenly drop dramatically below the minimum
level, see theWorkshop Manualfor diagnostic procedure.
Installation, Tightening and Alignment
Make sure the threads on the studs and nuts are clean to permit correct
torque when installing wheels. The mounting surfaces of rims, wheels,
spacer rings and clamps must be free of dirt, rust, lubricants or damage.
Use a wire brush to clean the mounting contact surfaces. Do not use
lubricant on threads.
Check the rim or wheel for proper alignment after it has been properly
tightened. Rotate the wheel with a piece of chalk attached to a steady,
firm surface, and placed to just barely clear the outside surface of the
tire bead seat; this procedure points out the high spot. A high spot does
not necessarily mean that the lug nuts have been unevenly tightened,
but could be the result of a bent wheel.
Use the following installation procedure:
1. Slide inner rear or front tire and wheel in position over studs and push
it back as far as possible. Use care so that the threads on the studs are
not damaged.
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Disc Wheel with Flange Nuts (Hub-piloted).
Front wheel mounting of flange nut
system.
A. Flange nut
B. Wheel(s)
C. Brake drum
D. Wheel stud (22 millimeter)
E. Wheel hub
2. Position the outer rear tire and wheel in place over the studs and
push it back as far as possible. Use care so that the threads on the studs
are not damaged.
Rear wheel mounting of flange nut
system.
A. Flange nut
B. Wheel(s)
C. Brake drum
D. Wheel stud (22 millimeter)
E. Wheel hub
Aluminum Rear Disc Wheel with Flange Nuts (Hub-piloted).
A. Flange nut
B. Wheel(s)
C. Brake drum
D. Wheel stud (22 millimeter)
E. Wheel hub
F. Wheel locator pad
A
BC
D
E
E
D
C
A
B
A
C
D
E
F
B
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Note for aluminum wheels:Clean each wheel locator pad on the hub
from all dirt, rust and foreign material prior to re-installing rear
aluminum hub-piloted wheels. Apply a light coat of chassis grease,
never-seize or disc brake corrosion control grease, only to the wheel
locator pad.
3. Run the nuts on the studs until they contact the wheel(s). Rotate the
wheel assembly a half-turn to permit the parts to seat.
4. Draw-up the nuts alternately following the crisscross sequence
illustrated under the following wheel tightening sequence illustrations.
Do not fully tighten the nuts. This allows uniform seating of the nuts and
makes sure even face-to-face contact of the wheel and hub.
8–lug wheel
10–lug wheel
5. Continue tightening the nuts to the torque specifications in the torque
chart using the same crisscross sequence shown.
6. After operating the vehicle approximately 50 miles (80 kilometers),
check the nuts for tightness. Some natural seating of parts may be
encountered and the torque on the nuts can drop. Retighten all nuts to
specifications.
Once a week, inspect and retighten the wheel stud nuts.
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