Diagnostic Information And Procedures; Brake Rotor Thickness Variation Check; Brake Rotor Lateral Runout Check; Brake Rotor Tolerance - GMC chervolet camaro 1999 Service Manual

5·58 Disc Brakes
Diagnostic Information and Procedures
Brake Rotor Thickness Variation Check
Measure the rotor thickness at four or more points
around the circumference of the rotor in order
to inspect the thickness variation. Use a micrometer
calibrated in ten-thousandths of an inch. Inspect each
measurement at the same distance from the edge
of the rotor.
A rotor that varies in thickness by more than 0.013 mm
(0.0005 in) may cause pedal pulsation or front end
vibration during brake applications. Refinish or replace
a rotor that does not meet the above specifications.
Brake Rotor Lateral Runout Check
Removal Procedure
Tools Required
J 8001 Dial Indicator Set
Notice: Any time the brake rotor is separated from the
wheel bearing flange, clean any rust or foreign
material from the mating surfaces of the wheel bearing
flange and the rotor. Failure to do so can result in
increased lateral runout of the rotor and brake
pulsation.
2
1. Clean the rotor surface (1).
Notice: Refer to Fastener Notice in Cautions and
Notices.
2. Reinstall the wheel nuts (2) in order to retain
the rotor.
Tighten
Tighten the wheel nuts in a star pattern to
140 N-m (100 lb ft).
181819
3. Fasten the J 8001 to the steering knuckle for front
or to the brake mounting flange on the rear axle
for rear so that the indicator button contacts
the rotor surface about 13 mm (0.5 in) from the
rotor edge.
Brakes
4. Set the J 8001 to zero.
5. Turn the rotor one complete revolution. Inspect
the runout indicated on the dial. If the TIR
. exceeds 0.15 mm (0.006 in), refinish or replace
the rotor.
In some cases, excessive lateral runout of the
rotor may be. improved by indexing the rotor on the
hub, one or two bolt positions from the original
position. Indexing the rotor requires removal and
installation of the front brake caliper. For
removal of the front brake rotor, refer to Brake
Rotor Replacement (Front). For rear brake
rotor replacement, refer to Brake Rotor
Replacement (Rear).
If the lateral runout cannot be corrected by
indexing the front rotor, inspect the hub and the
front wheel bearing for excessive lateral runout or
looseness. If the hub lateral runout exceeds
0.040 mm (0.015 in), replace the hub and bearing.
If
lateral runout of the hub and bearing is within
specifications, refinish or replace the rotor as
necessary.
If the lateral runout cannot be corrected by
indexing the rear rotor, inspect the rear axle shaft
flange for excessive lateral runout. If the axle
flange lateral runout exceeds 0.040 mm (0.015 in),
replace the axle shaft. If lateral runout of the
axle flange hub is within specifications, refinish or
replace the rotor as necessary.
Brake Rotor Tolerance
Tolerances of the braking surfaces for the following
conditions are held closely during the manufacture of
the brake rotor:
• Flatness
• Parallelism
• Lateral runout
The maintenance of close tolerances on the shape of
the braking surfaces is necessary in order to
prevent brake roughness or pulsation. The surface
finish must be hel.d to a specified range of a 60 degree
radius of roughness or less. A new rotor conforms
to the above specifications, as will a correctly
refinished rotor. For front brake rotors, refer to
Refinishing Brake Rotors (Front). For rear brake rotors,
refer to Refinishing Brake Rotors (Rear). Control of
the braking surface finish will eliminate the following
problems:
• Hard pedal application
• Excessive brake fade
• Pulls
• Erratic performance.
Control of the braking surface finish will improve
lining life.
Light scoring of the rotor surfaces not exceeding
1.5 mm (0.060 in) in depth is not detrimental to brake
operation. Normal use may cause light scoring.
(