GMC 1976 ZEO 6083 Maintenance Manual page 604

4. Continue to revolve wheel and check amount
of lateral run-out (amount of wheel side wobble).
This should not exceed 3/32-inch.
5. Place point of marker at inside of wheel at
point "B", in Figure 12 . Follow the previous proce-
dure to check radial run-out (out-of-round condi
tion); this should not exceed 3/32-inch. If wheel is
distorted beyond these dimensions it should be re-
placed .
6. If doubt exists whether the wheel or hub is
distorted, hub may be checked as follows: Replace
the existing wheel with a wheel known to be true.
Revolve the wheel and make the previously, men-
tioned tests. If tests are within limits, the hub is
satisfactory, but wheel is sprung.
7 . A dismounted wheel may be checked for side
wobble by placing a straight-edge on face or hub of
wheel. Measure distance from straight-edge to edge
of wheel rim, this should be checked at four equally
spaced locations. If distance is the same at all posi-
tions wheel is not distorted. (See figure 13) A dis-
mounted wheel may also be checked for radial, and
lateral run-out if desired, by temporarily mounting it
to a hub on vehicle. Follow the previous Steps 2, 3,
4, and 5.
WORN WHEEL STUD HOLES
(FIGURE 14)
This condition will usually be accompanied by
appearance of a shiny worn surface on wheel face,
indicating that loose wheels were moving against
each other. If the stud holes are out of shape - oval
or egg shaped - and where a build-up of metal is
around them, these wheels must be replaced .
CRACKED DISC WHEELS (FIGURE 14)
Cracks running from hand-hole to stud-hole or
bolt-hole to center-hole or hand-hole to hand-hole,
or hand-hole to rim. or stud-hole to stud-hole, are a
direct result of overloading. Check working loads of
vehicle, discard damaged wheels, check wheel studs
and complete assembly.
The hub assembly may have a worn mounting
face as a result of moving of the wheel on the hub.
WHEELS AND TIRES 10- 9
If Measurements Vary Over 3/32" Wheel
Is Distorted and Should Not Be Used
Figure 12-Method of Checking Distorted Wheels
The studs may have turned in the hub and worn the
stud groove or the studs may have actual cracks or
breaks resulting from this condition. The wheel may
have worn ball seats in the stud holes. All these
possibilities must be checked and all damaged parts
replaced .
RUST STREAKS ON DISCS EMANATING
FROM STUD HOLES
This is a positive indication that the cap nuts are,
or have been, loose. In this case, the assembly should
be checked carefully because damage to hub, studs,
or wheel may have been caused by running in this
condition.
Measurements should be taken at four
equally spaced locations around hub
of wheel
A-1939
Figure 13-Wheel Checking Diagram