UNDERCARRIAGE GRT880 SERVICE MANUAL
8-4
Published 10/19/2017, Control # 618-00
Wheels And Tires
Description
The standard tire size for this unit is 29.5 x 25.
Each wheel assembly (tire and rim) is mounted on the
planetary hub with 24 grade 8 lug nuts.
NOTE: The tire diameters, widths, and weights may vary
slightly depending on the tire manufacturer.
Off-highway tires are designed to operate with a certain
sidewall deflection or bulge. Correct air pressure ensures
prior deflection which, in turn, ensures proper traction,
flotation, support of load, and prevents excessive flexing of
the tire. Over inflation increases rim stresses, which results
in lowered rim life.
Refer to and adhere to the inflation pressures in the Load
Chart Book in the crane cab.
Maintenance
Mounting Wheel Assemblies
NOTE: Do not lubricate the wheel studs or lug nuts.
1. Raise the crane on outriggers so the wheels are off the
ground.
NOTE: Prior to wheel installation remove any dirt or grease
from wheel mounting surfaces.
2. Position the wheel assembly on the mounting studs.
Install the lug nuts and tighten them to 70 Nm (50 lb-ft) in
the sequence shown in Figure 8-2.
3. Ensure the wheel assembly is positioned properly on the
hub.
4. Continue to torque the lug nuts 407 Nm to 475 Nm
(300 lb-ft to 350 lb-ft) in the sequence shown in
Figure 8-2.
5. Lower the crane onto its tires. Retract and stow the
outrigger assemblies and the floats.
6. Retorque lug nuts after approximately one hour of travel.
Typical Wear Patterns
Incorrect Tire Pressure
Too high air pressure Figure 8-3, View 1) gives rapid wear in
the middle of the tire. Too low air pressure (Figure 8-3, View
2) gives rapid shoulder wear.
WARNING
Possible equipment damage and/or
personal injury!
Driving the crane with a tire under inflated at 80% or less
of its recommended pressure can cause the wheel and/or
tire to fail. Per OSHA Standard 1910.177(f)(2), when a tire
has been driven under inflated at 80% or less of its
recommended pressure, it must first be completely
deflated, removed from the axle, disassembled, and
inspected before re-inflation.
CAUTION
Do not mix tires or rims from different manufacturers.
Vehicle stability can be affected.
DANGER
Do not attempt to demount or mount tires without proper
training. The high pressures involved can cause tire and
rim parts and tools to fly with explosive force, if proper
procedures are not used, causing severe injury or death
to personnel and damage to the crane and surrounding
area.
Reference Only
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