GMC 1976 ZEO 6083 Maintenance Manual page 257

5- 3 8 BRAKES
Figure 52-Wear Indicators
CLEANING AND INSPECTION
1 . Thoroughly clean the holes and the bushing
grooves in the caliper ears . Wipe all dirt from the
mounting bolts. Do not use abrasives on the bolts
since this will damage the plating. If the bolts are
corroded, or damaged, they should be replaced .
2. Examine the inside of the caliper for evidence
of fluid leakage. -If leakage is noted, the caliper
should be overhauled . Wipe the inside of the caliper
clean, including the exterior of the dust boot . Check
the boot for cuts, cracks or other damage . Make sure
that the boot is properly engaged in the groove in the
piston and also in the caliper counter-bore . (figure
53)
CAUTION : Do not use compressed air to
clean the inside ofthe caliper since this may
cause the dust boot to become unseated.
DISC INSPECTION
Light scoring .010-.020 inch deep, of the disc
braking surface will normally occur during brake
application, turning is not required unless they are
Figure 53-Boot Installation
severely scored . It is not necessary to remove all
score marks when turning. Precision equipment
must be used when turning discs and the following
specifications must be carefully observed . DO NOT
reduce total thickness of the braking surface any-
more than the turning dimension of 1 .185" . If too
much is removed, even maximum pedal travel will
not apply the brakes if pads are worn .
Disc runout can be checked by clamping a dial
indicator to the caliper or plain arm so that the stylus
touches the disc about an inch from its outer edge .
Rotate disc and check indicator reading. If the lat-
eral runout exceeds specifications the disc should be
replaced or refinished .
After turning, brake surface thickness must not
vary more than .0005" . Lateral runout must not ex-
ceed specifications . Surface finish must be non-direc
tional and smoothness maintained at 30-50 micro
inches .
Figure 54-Discard Dimension (Disc)