Chevrolet Silverado / GMC Sierra. Service manual — part 1505

Ensure that the measurements are only taken within the friction surfaces and that the
micrometer is positioned the same distance from the outer edge of the rotor, about 13 mm
(1/2 in), for each measurement.

4. Calculate the difference between the highest and lowest thickness measurement recorded to

obtain the amount of thickness variation.

5. Compare the thickness variation measurement to the following specifications:

Specification - JD9, JF3, JF7, JH6, JH7 Front and JH6, JH7 Rear: Brake rotor
maximum allowable thickness variation: 0.025 mm (0.001 in)

Specification - JD9 Rear: Brake rotor maximum allowable thickness variation:
0.009 mm (0.0004 in)

6. If the brake rotor thickness variation measurement exceeds the specification, the rotor

requires refinishing or replacement.

BRAKE ROTOR SURFACE AND WEAR INSPECTION

1. If the inboard friction surface of the brake rotor is not accessible, reposition and support the

caliper with the brake pads. Refer to Front Disc Brake Pads Replacement (JH6, JH7) or
Front Disc Brake Pads Replacement (JD9, JF3, JF7) and/or Rear Disc Brake Pads
Replacement (JH6, JH7) or Rear Disc Brake Pads Replacement (JD9).

2. Clean the friction surfaces of the brake rotor with denatured alcohol, or an equivalent

approved brake cleaner.

3. Inspect the friction surfaces of the brake rotor for the following Braking Surface

Conditions:

Heavy rust and/or pitting

Light surface rust can be removed with an abrasive disc. Heavy surface rust and/or
pitting must be removed by refinishing the rotor.

IMPORTANT: Whenever a brake rotor is refinished or replaced, the

assembled lateral runout (LRO) of the rotor must be
measured to ensure optimum performance of the disc
brakes.

CAUTION: Refer to Brake Dust Caution .

2008 Chevrolet Silverado 1500

2008 BRAKES Disc Brakes - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

Cracks and/or heat spots

Excessive blueing discoloration

4. If the friction surfaces of the brake rotor exhibit one or more of the Braking Surface

Conditions, the rotor requires refinishing or replacement.

2008 Chevrolet Silverado 1500

2008 BRAKES Disc Brakes - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

Fig. 3: Measuring Brake Rotor Thickness
Courtesy of GENERAL MOTORS CORP.

5. Using a micrometer calibrated in thousanths-of-a-millimeter, or ten-thousanths-of-an-inch,

measure and record the scoring depth of any grooves present on the rotor friction surfaces.

6. Compare the groove scoring depth recorded to the following specification:

Specification: Brake rotor maximum allowable scoring: 1.50 mm (0.059 in)

7. If the brake rotor scoring depth exceeds the specification, or if an excessive amount of

scoring is present, the rotor requires refinishing or replacement.

BRAKE ROTOR ASSEMBLED LATERAL RUNOUT MEASUREMENT

Tools Required

J 39544-KIT Torque-Limiting Socket Set, or equivalent. See Special Tools.

J 41013 Rotor Resurfacing Kit. See Special Tools.

J 42450-A Wheel Hub Resurfacing Kit. See Special Tools.

J 45101 Hub and Wheel Runout Gage. See Special Tools.

J 45101-100 Conical Brake Rotor Washers. See Special Tools.

1. Matchmark the position of the brake rotor to the wheel studs if this has not been done

already.

CAUTION: Refer to Brake Dust Caution .

IMPORTANT:

Brake rotor assembled lateral runout (LRO) exceeding the
maximum allowable specification can cause thickness
variation to develop in the brake rotor over time, usually
between 4 800-11 300 km (3,000-7,000 mi).

Brake rotor thickness variation MUST be checked BEFORE
checking for assembled lateral runout (LRO). Thickness
variation exceeding the maximum acceptable level can cause
brake pulsation. Refer to Brake Rotor Thickness Variation
Measurement.

2008 Chevrolet Silverado 1500

2008 BRAKES Disc Brakes - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

2. Inspect the mating surface of the hub/axle flange and the brake rotor to ensure that there are

no foreign particles, corrosion, rust, or debris remaining. If the wheel hub/axle flange and/or
if the brake rotor mating surfaces exhibit these conditions, perform the following steps:

1. Remove the brake rotor from the vehicle. Refer to Front Brake Rotor Replacement

(JH6, JH7)Front Brake Rotor Replacement (JD9, JF3, JF7) and/or Rear Brake
Rotor Replacement (JD9)Rear Brake Rotor Replacement (JH6)Rear Brake
Rotor Replacement (JH7) .

2. Using the J 42450-A , thoroughly clean any rust or corrosion from the mating surface

of the hub/axle flange. See Special Tools.

3. Using the J 41013 , thoroughly clean any rust or corrosion from the mating surface of

the brake rotor. See Special Tools.

4. Clean the friction surfaces of the brake rotor with denatured alcohol, or an equivalent

approved brake cleaner.

3. Install the rotor to the hub/axle flange using the matchmark made prior to removal.

IMPORTANT: Whenever the brake rotor has been separated from the

hub/axle flange, any rust or contaminants should be cleaned
from the hub/axle flange and the brake rotor mating surfaces.
Failure to do this may result in excessive assembled lateral
runout (LRO) of the brake rotor, which could lead to brake
pulsation.

2008 Chevrolet Silverado 1500

2008 BRAKES Disc Brakes - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado