Jeep 1996 Grand Cherokee Service Manual - page 159
REAR DISC BRAKE ROTOR
ROTOR MINIMUM THICKNESS
Minimum usable thickness of the rear disc brake
rotor is 9.5 mm (0.374 in.). The thickness specifica-
tion is located on the edge of the parking brake drum
section of the rotor (Fig. 12).
Never resurface a rotor if machining would cause
thickness to fall below this limit.
Measure rotor thickness at the center of the brake-
shoe contact surface. Replace the rotor if worn below
minimum thickness, or if refinishing would reduce
thickness below the allowable minimum.
REAR ROTOR THICKNESS VARIATION
Variations in rotor thickness will cause pedal pul-
sation, noise and shudder.
Measure rotor thickness at four to six points
around the rotor face. Position the micrometer
approximately 3/4 inch from the rotor outer circum-
ference for each measurement (Fig. 10).
Thickness should not vary by more than 0.0254
mm (0.001 in.) from point to point on the rotor.
Refinish or replace the rotor if necessary.
REAR ROTOR LATERAL RUNOUT
Check rotor lateral runout whenever diagnosis
indicates pedal pulsation and rapid, uneven brakelin-
ing wear.
The rotor must be securely clamped to the hub to
ensure an accurate runout measurement. Secure the
rotor with the wheel nuts and 4 or 5 large diameter
flat washers on each stud.
Use a dial indicator to check lateral runout (Fig.
11). Maximum allowable lateral runout is 0.13 mm
(0.005 in.).
PARKING BRAKE
NOTE: Parking brake adjustment is controlled by a
cable tensioner. Once the tensioner is adjusted at
the factory, it should not require further attention.
However, there are two instances when adjustment
will be required. The first is when a new tensioner,
or cables have been installed. And the second, is
when the tensioner and cables are disconnected for
access to other brake components.
The parking brake switch is in circuit with the red
warning lamp in the dash. The switch will cause the
lamp to illuminate only when the parking brakes are
applied. If the lamp remains on after parking brake
release, the switch or wires are faulty, or cable ten-
sioner adjustment is incorrect.
Fig. 10 Measuring Rotor Thickness Variation
Fig. 11 Checking Rotor Lateral Runout
Fig. 12 Thickness Specification On Rear Rotor
5 - 10
BRAKES
ZJ
DIAGNOSIS AND TESTING (Continued)