Check to make sure that the axle mounting U-bolt nuts, attaching or
mounting bolts and nuts are securely tightened. Regularly check front
axle for damage, binding, worn parts and adequate lubrication.
At regular intervals, or during other scheduled maintenance, (tire
rotation/service, wheel bearing service, alignment, etc.) the kingpins
should be checked for excessive wear. Refer to the service manual for
proper procedures.
Toe-in setting - general inspection
Inspecting steer axle tires in the first 3,000–10,000 service miles
(4,800–16,000 service km) will generally show if tires are wearing
normally.
Rapid outside shoulder wear on both tires indicates too much toe-in.
Rapid inside shoulder wear on both tires indicates too much toe-out. In
P&D-type service, left-to-right steer tire tread life differentials up to 40%
can be observed depending on routes and other variables.
Follow the tire manufacturer’s recommended cold inflation pressure for
the tire size, load range (ply rating) and steer axle loading typical for
their operation (each steer axle tire will equal
1 2steer axle loading).
Special applications may warrant a setting based on past experience with
the type of tire operating loads and conditions. Radial tires are more
sensitive to toe-in setting than bias ply tires. While not insensitive to
vehicle alignment, fine tuning school bus alignment to line-haul truck
standards will not drastically improve tire tread life.
It is essential that correct toe-in and tire pressure be maintained for
optimum tire wear.
Rear axle - general inspection
Check to make sure that the axle mounting U-bolts, attaching or
mounting bolts and nuts are securely tightened. Refer toU-bolt nut
torquein this chapter. Regularly check the rear axle for damaged,
binding or worn parts.
NoSpin Detroit Locker positive locking differential
Vehicles equipped with this type differential have the operator’s manual
supplied with the vehicle. Refer to this manual for maintenance checks.
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Do not manually adjust the automatic slack adjusters to correct
excessive pushrod stroke as it may result in reduced brake
effectiveness and a vehicle crash. Excessive pushrod stroke indicates
that a problem exists with the automatic adjuster, with the installation
of the adjuster, or with foundation brake components that manual
adjustment will not remedy. Seek service from a qualified facility for
excessive pushrod stroke.
Inspect the brake lining every maintenance interval. When brake lining or
blocks are worn to within 1/16 inch (1.6 mm) of rivets, brake lining must
be replaced. This inspection or adjustment should only be performed by
a qualified technician and must be in accordance with instructions
provided by the service manual.
Do not back off or disconnect the front brakes so that they are less
effective, letting the rear brakes do all the stopping of the vehicle. Do
not overlook the brakes on the trailer, either. Brake condition on the
trailer is just as important as the tractor. Proper brake balance on trucks
and tractor-trailers is essential for effective braking.
Once a year, the entire brake system must be inspected. Check the
following:
• Any rubber as it may deteriorate whenever used. Rubber brake
components should be inspected by a qualified technician and
replaced as necessary. Replacement intervals vary according to the
severity and length of vehicle service.
• Condition of brake drums, brake chambers and slack adjusters.
• System for air leaks.
• Hose or pipes for rust, damage and deterioration.
• Operation of service and parking brakes.
Some parts such as air brake chamber diaphragm, air compressor and air
cleaner should be inspected periodically and replaced if considered
unserviceable.
Air brakes - air dryer
Performance of desiccant or after-cooler type air dryers is dependent on
climatic conditions in which your vehicle is operating. Maintenance
schedules must be established for each specific operation.
The use of an air dryer on a vehicle does not eliminate the need to
periodically drain the air reservoirs.
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WHEELS
General
Wheel bearings should be inspected, lubricated and adjusted at regular
intervals. This is especially important if operating in deep sand, mud, or
water. Refer toLubricant specificationsin this chapter.
When installing wheel balance weights, they must be mounted on the
dome-side of the wheel only. Failure to do so may result in loss of wheel
weight and/or damage to brakes or wheels.
Important:Remember to replace the wheel air valves when the road
tires are replaced at the end of their useful life.
Oil lubricated front wheel bearings
During normal vehicle duty cycle, the lube 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:
•a slit or small hole in the rubber check vent or
•the window
You can use either of these methods to prevent pressure build-up.
Normal maintenance
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 ensures that the lube level can be easily
observed through the clear window as intended. In situations where the
window is clean on the outside but discolored on the inside, the lube
level may be checked by inserting a finger through the rubber check
vent hole.
The specified lube level for a clear window type hubcaps is from the
minimum line to + 5/16 inch above the minimum line.
If the lube level should suddenly drop dramatically below the minimum
level, see the Service Manual for diagnostic procedure.
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light coat of chassis grease, never-seize or disc brake corrosion control
grease, only to the wheel locator pad.
When installing the tire and rim assembly on disc-brake equipped axles,
make sure the tire valve stem clears the brake caliper. The use of a tire
manufacturer’s stem forming tool is the only acceptable method of
obtaining clearance when necessary.
Note:Always observe the following instructions:
Failure to follow these instructions could result in property
damage, personal injury or death
•Always loosen rim clamps before complete removal of nut from stud
(cast spoke wheels). With loosened nuts on stud, strike clamps with a
heavy hammer and be sure each clamp is loose.
•Always deflate tires completely before removing locks or side rings.
•Always inflate tires in a safety cage.
•Never mix rim side rings or lock rings of different types,
manufacturers or sizes.
•Never use cracked, bent or badly rusted parts.
•Never re-inflate flat tires on-vehicle; use the spare tire.
•Never add air until each side ring or lock ring is fully seated.
•Never hammer side ring or lock ring on a partially- or fully-inflated
tire.
Proper torque
It is important to tighten and maintain wheel and rim mounting nuts to
the proper torque. Loose nuts or over-tightened nuts can lead to
premature wear and possible failure of the wheel and/or mounting
hardware.
Changing wheel types
Consult your dealer or wheel/rim distributor before attempting any wheel
or fastener changes.
Use only the same type and style wheels and mounting hardware
to replace original parts. Failure to do so may result in an
assembly that looks fine, but does not fit together properly. This could
possibly cause wheel or fastener failures which could result in property
damage, personal injury or death.
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Tire sizeLoad
rangeApproved
rim widthsAxle capacity
Front - lb.
(kg)/psi
(kPa)Rear - lb.
(kg)/psi
(kPa)
295/75R22.5 G 8.25, 9.0012350 (5602) /
110 (758)23900 (10841)
/ 100 (690)
295/80R22.5 H8.2514400 (6531) /
120 (827)27760 (12591)
/ 120 (827)
9.0014780 (6704) /
120 (827)27760 (12591)
/ 120 (827)
Tire inflation information
All tires with Steel Carcass Plies (if equipped):
This type of tire utilizes steel cords in the sidewalls. As such, they
cannot be treated like normal light truck tires. Tire service, including
adjusting the air pressure, must be performed by personnel trained,
supervised and equipped according to Federal Occupational Safety and
Health Administration (OSHA) regulations. For example, during any
procedure involving tire inflation, the technician or individual must
utilize a remote inflation device, and ensure that all persons are clear of
the trajectory area.
WARNINGAn inflated tire and rim can be very dangerous if
improperly used, serviced or maintained. To avoid serious injury,
never attempt to re-inflate a tire which has been run flat or seriously
under-inflated without first removing the tire from the wheel assembly
for inspection. Do not attempt to add air to tires or replace tires or
wheels without first taking precautions to protect persons and
property.
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