Pontiac FIREBIRD 1972 Service Manual page 510

DISC BRAKES 5E- 15
close, and even small deviations may cause a brake vibra-
tion. A rotor that does not meet the specifications must be
discarded and replaced with a new rotor, or machined to
specification.
SURFACE TOLERANCE AND FINISH
Improper surface finish will shorten lining life. Differ-
ences in finish smoothness between rotors may cause a
brake pull. Surface finish can not be measured with nor-
mal service equipment.
Light scoring of the rotor surfaces not exceeding 0.015"
in depth, which may result from normal use, is not detri-
mental to brake operation.
THICKNESS
Measure thickness with a micrometer.
NOTE: When total rotor thickness is less than
.965" (A, F and G Series) or 1.215" (B Se-
ries), rotor must be replaced. If rotor is too thin,
the linings may dislodge.
SERVICE
Extremely close control of the disc rubbing surfaces is
necessary. The specification for parallelism of the two
rotor faces is particularly critical with regard to brake
roughness. Differences in finish smoothness between ro-
tors will cause a brake pull. If the rotor is too thin, the
linings may become dislodged.
Because of the accuracy required, refinishing of the rub-
bing surface is not recommended unless precision equip-
b
/
DO NOT USE FLAT ADAPTES
USE ADAPTERS
THAT MOUNT ON
BEARING SURFACE
D O N O T USE ADAPTORS
WHICH MOUNT O N FLAT
SURFACE O F RACE
1
MIN. THICKNESS
I ,215"-PONTIAC
Fig. 5E-22 Disc Rotor Turning
ment is available and surfaces can be held within
specifications listed. Specifically, adapters which mount
against the bearing surface of the race should be used, as
it has been found that other adapters actually put runout
into the rotor (Fig. 5E-21 and 5E-22).
When turning rotors, it is very important that BOTH sides
be turned. It is not necessary, however, that equal
amounts be removed from each side. Always remove as
little metal as possible.
Disc turning is primarily for correction of bad runout or
parallelism. Turning to correct minor scoring is also ac-
ceptable provided the disc is not turned below the mini-
mim thickness.
SWITCH TERMINAL
REAR MASTER CYLINDER
\
I N F T PORT
FRONT MASTER CYLINDER
I
INLET PORT
UTLET PORT TO
REAR BRAKES
OUTLET PORT
FRONT BRAK
Fig. 5E-21 Disc Rotor Turning Adaptors
- - - - - - -
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Fig. 5E-23 Combination Valve