Disc Refinishing; Brake Adjuster Access Hole; Unhooking Pull Back Spring; Minimum Requirements - Chevrolet 10 1971 Series Chassis Service Manual

IN SPE C T IO N HOLE
ADJU STM EN T A C C E S S HOLE
Fig. 26— Brake Adjuster Access Hole
2. Check the mounting bolts for corrosion or other
damage. Do not attempt to clean up the bolts. If they
appear corroded - replace them.
3. Carefully examine the outside surface of the piston
for scoring, nicks, corrosion and worn or damaged
chrome plating. If any surface defects are detected,
replace the piston.
The piston outside diameter is the pri­
NOTE:
mary sealing surface in the caliper assembly.
It is manufactured and plated to close toler­
ances. Refinishing by any means or the use of
any abrasive is not an acceptable practice.
4. Check the bore in the caliper for the same defects
as the piston. The piston bore, however, is not
plated and stains or minor corrosion can be polished
with crocus cloth.
Do not use emery cloth or any other form
NOTE:
of abrasive and thoroughly clean the caliper after
the use of crocus cloth. If the bore cannot be
cleaned up in this manner, replace the caliper.
Reassembly (Figs. 23 and 24)
1. Lubricate the caliper piston bore and the new piston
seal with clean brake fluid. Position the seal in the
caliper bore groove.
2. Lubricate the piston with clean brake fluid and
assemble a new boot into the groove in the piston so
that the fold faces the open end of the piston.
3. Insert the piston into the caliper bore using care not
to unseat the seal and force (50 to 100 pounds force
required) the piston to the bottom of the bore.
4. Position the dust boot in the caliper counterbore and
seat using boot installer Tool J-22904.
Check the boot installation to make sure
NOTE:
that the retaining ring moulded into the boot is
not bent and that the boot is installed below the
caliper face and evenly all around. If the boot is
not fully installed, dirt and moisture may enter
the bore and cause damage or corrosion.
5. Install the brake hose in the caliper inlet using a
new copper gasket.
C O V E R S R EM O V E D
FOR CLARITY
Installation
accurate control of the disc tolerances is necessary to
ensure proper brake operation.

Minimum Requirements

1. Must be flat within .002 T.I.R.
2. Must be parallel with each other within .003 T.I.R.
3. Total circumferential thickness variation at any
4. When mounted on bearing cups, lateral run-out must
5. Both surfaces must be free of scratch marks and
6. Finish is to be 20-60 micro inches and must not be
7. Both surfaces must be square with bearing cup
Fig. 27— Unhooking Pull Back Spring
Installation of the caliper and mounting
NOTE:
parts (rubber bushings, sleeves, bolts, and shoe
and lining assemblies) is the same as for: Brake
Shoes and Linings - except for the steps given
below.
1. Connect the brake hose to the brake line at
the frame bracket.
2. Bleed the calipers using the method outlined
in the beginning of this section.

DISC REFINISHING

Servicing of the brake disc is extremely critical since
All brake disc have a minimum thickness
NOTE:
dimension cast into them. This dimension is the
minimum wear dimension and not a refinish
dimension. Do not refinish a brake disc that will
not meet the specifications as shown below
after refinishing.
MINIMUM THICKNESS
AFTER REFINISHING
1.230
when checked radially.
radius must not exceed .0005 in 360°.
not exceed .005 T.I.R. and maximum rate of change
must not exceed .001 in 30°.
porosity.
circumferential (directional).
centerline within .003 T.I.R.
BRAKES 5-11
DISCARD
THICKNESS
1.215
10-30 CHEVROLET TRUCK SERVICE MANUAL