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22-2
WHEELS, BEARINGS AND TIRES
SERVICE PROCEDURES
WHEEL AND TIRE RUNOUT
Wheels and tires may be measured for both radial
and lateral runout. Radial runout (eccentricity) is the
difference between the high and low points
on
the
tread of the tire; while lateral runout is the "wobble"
of
the wheel and/or
tire.
Fig. I-Safety
Type Rim
Prior to measuring wheel and tire for runout, the
face of the hub at the mounting bolts should be meas-
ured for runout. The car should be driven a short dis-
tance before the measurement is made so that "flat-
spotting" of the tire (from being parked) does not af-
fect the runout measurement.
(1)
Attach dial indicator
C-3339
to a firm base so it
will be held steady while taking runout readings.
(2)
Place plunger of the dial indicator against one
of the center ribs of the tire tread and rotate the
wheel slowly to measure radial runout. This measure-
ment should not exceed
.060
inch.
(3)
To measure lateral runout (wobble), position
the dial indicator against the side of the tire.
This
measurement should not exceed .080 inch.
Rotating the tire on the wheel may reduce the run-
out or it may be necessary to take dial indicator meas-
urements of the wheel itself in order to determine
which unit has the excessive runout. Since the ex-
terior surfaces of the wheel rim may have paint runs
or bubbles, scratches or other imperfections it is bet-
ter to dial indicate the protected areas "A" and
"B"
(Fig.
2).
The radial runout, "A" should not exceed
.050
inch. The lateral runout (wobble), "B," should
not exceed .050 inch.
NOTE:
Under
no
circumstances should point indi-
cated by
"C" be
used for measuring runout as this
metal has been sheared in the manufacturing proc-
ess and
i s
not an even surface.
Fig. 2-Runout
Checking Area
WHEEL BALANCE
The need for balancing the wheels is indicated by
heavy vibration of the steering wheel of the car when
driving at speeds above 40 miles an hour over a
smooth straight highway.
Static (still) balance is equal distribution of the
weight of the wheel and tire around the spindle, in
such a manner that the wheel assembly has no tend-
ency to rotate by itself, regardless of its position. A
wheel that has a heavy spot is statically out of bal-
ance, resulting in a "hopping"
or
bouncing action.
A wheel and tire, to be in dynamic balance, must
first
be in static balance and also be in balance from
side to side when the wheel is at right angles to the
axis of rotation. A wheel not in dynamic balance
tends to wobble or shimmy.
Correction for static unbalance is made by
first
finding the location of the heavy spot, then adding
sufficient weight to counterbalance it at a location op-
posite the heavy section. (Follow the equipment man-
ufacturers recommendations. The total weight to be
added, should be divided in half and the weights
placed on the inside and outside rim edges.)
FRONT WHEEL BEARINGS
Removal
of the floor.
nut lock and the bearing adjusting nut.
(1)
Raise the car
so
that the front wheels are free
(2)
Remove the wheel cover, grease cap, cotter pin,
(3) Remove the thrust washer and outer bearing.
(4)
Slide the wheel, hub and drum assembly off the
(5) Drive out the inner oil seal and remove the
spindle.
bearing cone.
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