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MAINTENANCE AND LUBRICATION
Tire Maintenance
Tire Inflation
Tire inflation will cause tire to ground contact
characteristics as shown in Figure 4-18. Tire inflation
should be checked daily while the tire is cold, and during
road stops. Checking the tire pressures while tires are
hot will give a faulty increased pressure reading.
Adjusting tire air pressure to the specified amount while
tires are hot will produce improper tire to road contact
and thus abnormal wear. Do not exceed cold inflation
pressure listed on the semitrailer VIN plate located on the
front of the trailer. Exceeding cold inflation pressure will
result in damaged tire bodies, rims, and wheels. Replace
all valve stem caps when pressure checking/adjusting
has been completed. Remove any foreign objects from
between duals.
Tire Matching
Both tires on the same spindle must be the same size in
order to properly distribute the load and braking forces
between them. The tire must be mounted on a rim and
properly inflated before measuring. If there is an
allowable difference in size the smaller tire should be
mounted to the inside position of the duals.
Tape Measuring Method
Measure around each tire on the tread surface. A
maximum difference of 3/4" is allowed between the two
mating tires of a dual (See Figure 4-19.)
Straight Edge or String Method
(This method cannot be used if tire and wheel
assemblies are not mounted on the axle.) Jack trailer up
until the wheels are off of the ground. Hold a straight
edge against the tires of both ends of an axle. A gap at
one tire indicates a smaller tire. A maximum of 1/8" gap is
allowed (See Figure 4-20.)
4-28
Figure 4-18: Tire Inflation Examples
Figure 4-19: Measuring Tape Method
Figure 4-20: Straight Edge Method
STRAIGHT EDGE
F-618-0911 Edition
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