Cadillac 60 Series 1963 Shop Manual page 34

CHASSIS SUSPENSION
4-11
it
H
V
HI
I Dial Indicator L
Support J-6126 V ,
1 ^ ( Dial Indicator J-8001 | i
I
1
Fig. 4-14 Checking Lateral Runout at Bead Seat
7. Check radial wheel runout at bead seat by
positioning Dial Indicator Extension on bottom
face of rim bead seat (90° from felloe band) Fig.
4-15. Set indicator at zero. Rotate tire and wheel
assembly, note and record amount of runout.
Mark rim where minimum and maximum runout
occurs. Maximum runout as measured on rim
bead seat should not exceed .035 inch.
8. Rotate tire with respect to rim so that max-
imum runout point of tire, as marked on tire in
Steps 3 and 5 is at minimum runout point of the
wheel, or vice versa. This correction should be
performed for whichever condition (lateral or
radial) is most severe.
X
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1
^ ^
^Dial
Dial"
Indicator
. ". J
Indicator
Support
in
Fig. 4-15 Checking Radial Runout at Bead Seat
NOTE: To rotate tire with respect to rim,
it is necessary to remove tire and wheel as-
sembly from car, deflate tire, break bond
between bead seat and wheel, and then rotate
tire as required.
9. Reinstall tire and wheel assembly on brake
drum, aligning marked wheel stud and bolt hole.
10. Repeat total runout check procedures as
described in Steps 3 and 5 to make certain that
runout is within specifications. If runout is still
not within specifications, rotate wheel assembly
around mounting studs as previously described.
If proper runout for tire and wheel assembly
cannot be obtained by performing above checks,
and runout: measurements show that wheel is
within specifications, runout may be due to ex-
cessive tire runout, bolt circle runout, and/or
wheel flange runout. If wheel flange or bolt circle
is not the cause of excessive runout, it is an in-
dication that the tire is responsible and it should
be replaced.
If wheel runout measurements as made on car
are excessive, and total tire and wheel runout
cannot be reduced by the above procedures, the
wheel should be replaced.
g. Wheel and Tire Balance
Wheel, tire, and brake drum balance must be
maintained within certain limits, otherwise wheel
tramp and high speed shimmy may result.
Front wheel tramp and front wheel shimmy are
two entirely different conditions. Front wheel
tramp, which usually occurs at high speed, is a
condition in which a pair of wheels hop in opposite
phase. It is caused by static unbalance of the
wheels or drums, loose linkage in the front end,
or improperly operating shock absorbers.
Shimmy may occur at lower speeds. It is a
self-excited oscillation about the steering axis
of the front wheels, caused by dynamic unbalance
of the wheels or drums, loose or worn front end
linkage, loose or worn steering gear parts, or
faulty steering gear adjustment. Tramp and
shimmy will be felt in the entire car, but shimmy
can also be felt at the steering wheel. Shimmy
is a front wheel condition entirely, whereas it is
possible to have tramp in front or rear wheels.
A wheel and tire assembly may lose its original
balance due to normal seating-in and break-in,
irregular tread wear, or tire repair. Consequent-
ly, if front end instability develops, the tire and
wheel assembly should be checked for static
balance, in addition to checking steering gear
adjustment and radial runout of the wheel and
tire assembly. The assembly should also be
checked for balance whenever tires are replaced,