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Disc Brake System: Other Chevrolet Silverado Classic 1500

Mechanical - Hydraulic ~1144 words

Brake Rotor Thickness Measurement

CAUTIONRefer to Brake Dust Caution .
  1. Clean the brake pad lining contact surface of the brake rotor with denatured alcohol or an equivalent brake cleaner.
  2. Using a calibrated micrometer measure and record the lowest thickness of the brake rotor at 4 or more points equally spaced around the rotor. Ensure that the measurements are only taken within the brake pad lining contact area and that the micrometer is positioned the same distance from the outside edge of the rotor for each measurement.
  3. Compare the lowest thickness measurement recorded to the following specifications: Specification - Front Brake (RPO JC4): Rotor minimum allowable thickness after refinishing 28. 0 mm (1. 10 in) Rotor discard thickness 27. 50 mm (1. 082 in) Specification - Front Brake (RPOs JF3/JF7): Rotor minimum allowable thickness after refinishing 28. 0 mm (1. 10 in) Rotor discard thickness 28. 0 mm (1. 10 in) Specification - Front Brake (RPO JH1): Rotor minimum allowable thickness after refinishing 28. 0 mm (1. 10 in) Rotor discard thickness 27. 50 mm (1. 082 in) Specification - Front Brake (RPOs JH6/JH7): Rotor minimum allowable thickness after refinishing 37. 0 mm (1. 46 in) Rotor discard thickness 36. 50 mm (1. 437 in) Specification - Rear Brake (RPO JC4): Rotor minimum allowable thickness after refinishing 29. 0 mm (1. 142 in) Rotor discard thickness 28. 50 mm (1. 122 in) Specification - Rear Brake (RPO JH1): Rotor minimum allowable thickness after refinishing 19. 0 mm (0. 748 in) Rotor discard thickness 18. 50 mm (0. 728 in) Specification - Rear Brake (RPO JH6): Rotor minimum allowable thickness after refinishing 28. 0 mm (1. 102 in) Rotor discard thickness 27. 50 mm (1. 082 in) Specification - Rear Brake (RPO JH7): Rotor minimum allowable thickness after refinishing 29. 0 mm (1. 142 in) Rotor discard thickness 28. 50 mm (1. 122 in)
  4. If the lowest thickness measurement of the brake rotor is above the minimum allowable thickness after refinishing specification; the rotor may be able to be refinished, depending upon surface and wear conditions which may be present.
  5. If the lowest thickness measurement of the brake rotor is at or below the minimum allowable thickness after refinishing specification; the rotor may not be refinished.
  6. If the lowest thickness measurement of the brake rotor is at or below the discard thickness specification; the rotor requires replacement.

Brake Rotor Thickness Variation Measurement

CAUTIONRefer to Brake Dust Caution .
IMPORTANTAny disc brake rotor that exhibits thickness variation exceeding the maximum acceptable level must be refinished or replaced. Thickness variation exceeding the maximum acceptable level can cause brake pulsation.
  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 (1500 Series)»(ref-277897-S42462250402008012100000) or «Front Disc Brake Pads Replacement (25/3500 Series)»(ref-277897-S19510257572008012100000) and/or «Rear Disc Brake Pads Replacement (1500 Series)»(ref-277897-S40260797072008012100000) or «Rear Disc Brake Pads Replacement (25/3500 Series)»(ref-277897-S24596849302008012100000) .
  2. Clean the friction surfaces of the brake rotor with denatured alcohol, or an equivalent approved brake cleaner.
  3. Using a micrometer calibrated in thousanths-of-a-millimeter, or ten-thousanths-of-an-inch, measure and record the thickness of the brake rotor at four or more points, evenly spaced around the rotor. 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 measurements recorded to obtain the amount of thickness variation.
  5. Compare the thickness variation measurement to the following specification: Specification: Brake rotor maximum allowable thickness variation: 0. 025 mm (0. 001 in)
  6. If the brake rotor thickness variation measurement exceeds the specification, the rotor requires refinishing or replacement.

Brake Pad and Rotor Burnishing

CAUTIONRefer to ROAD TEST CAUTION .

Burnishing the brake pads and brake rotors is necessary in order to ensure that the braking surfaces are properly prepared after service has been performed on the disc brake system.

This procedure should be performed whenever the disc brake rotors have been refinished or replaced, and/or whenever the disc brake pads have been replaced.

  1. Select a smooth road with little or no traffic.
  2. Accelerate the vehicle to 48 km/h (30 mph). IMPORTANT: Use care to avoid overheating the brakes while performing this step.
  3. Using moderate to firm pressure, apply the brakes to bring the vehicle to a stop. Do not allow the brakes to lock.
  4. Repeat steps 2 and 3 until approximately 20 stops have been completed. Allow sufficient cooling periods between stops in order to properly burnish the brake pads and rotors.

Brake Rotor Refinishing

Tools Required

  1. J 41013 Rotor Resurfacing Kit. See «Special Tools»(ref-277897-S30276597702008012100000) .
  2. J 42450-A Wheel Hub Resurfacing Kit. See «Special Tools»(ref-277897-S30276597702008012100000) .
CAUTIONRefer to Brake Dust Caution .
IMPORTANTThe disc brake rotors do not require refinishing as part of routine brake system service. New disc brake rotors do not require refinishing. Do not refinish disc brake rotors in an attempt to correct the following conditions: Brake system noise - squeal, growl, groan Uneven and/or premature disc brake pad wear Superficial or cosmetic corrosion/rust of the disc brake rotor friction surface Scoring of the disc brake rotor friction surface less than the maximum allowable specification Before refinishing a brake rotor, the rotor MUST first be checked for adequate thickness to allow the rotor to be refinished and remain above the minimum allowable thickness after refinish specification. Refer to Brake Rotor Thickness Measurement . Disc brake rotors should only be refinished if they have adequate thickness to be refinished and if one or more of the following conditions exist: Thickness variation in excess of the maximum allowable specification Excessive corrosion/rust and/or pitting Cracks and/or heat spots Excessive blueing discoloration Scoring of the disc brake rotor surface in excess of the maximum allowable specification Disc brake rotors may need to be refinished as part of the process for correcting brake rotor assembled lateral runout (LRO) that exceeds the maximum allowable specification.
IMPORTANTIf the vehicle is equipped with cross-drilled rotors, use a lathe with positive rake tooling. This setup requires less cutting pressure, which will result in less vibration, and a better surface finish. Also, use a vibration dampener when cutting. Otherwise, refinish according to the following instructions.
  1. Using the J 42450-A , thoroughly clean any rust or corrosion from the mating surface of the hub/axle flange. See «Special Tools»(ref-277897-S30276597702008012100000) .
  2. Using the J 41013 , thoroughly clean any rust or corrosion from the mating surface and mounting surface of the brake rotor. See «Special Tools»(ref-277897-S30276597702008012100000) .
  3. Inspect the mating surfaces of the hub/axle flange and the rotor to ensure that there are no foreign particles or debris remaining.
  4. Mount the brake rotor to the brake lathe according to the lathe manufacturer's instructions, ensuring that all mounting attachments and adapters are clean and free of debris.
  5. Ensure that any vibration dampening attachments are securely in place.
  6. With the brake lathe running, slowly bring in the cutting tools until they just contact the brake rotor friction surfaces.
  7. Observe the witness mark on the brake rotor. If the witness mark extends approximately three-quarters or more of the way around the brake rotor friction surface on each side, the brake rotor is properly mounted to the lathe.
  8. If the witness mark does not extend three-quarters or more of the way around the brake rotor, re-mount the rotor to the lathe.
  9. Following the brake lathe manufacturer's instructions, refinish the brake rotor.
  10. After each successive cut, inspect the brake rotor thickness. Refer to «Brake Rotor Thickness Measurement»(ref-277897-S11119211882008012100000) .
  11. If at any time the brake rotor exceeds the minimum allowable thickness after refinish specification, the brake rotor must be replaced.
  12. After refinishing the brake rotor, use the following procedure in order to obtain the desired non-directional finish: Follow the brake lathe manufacturer's recommended speed setting for applying a non-directional finish. Using moderate pressure, apply the non-directional finish: If the lathe is equipped with a non-directional finishing tool, apply the finish with 120-grit aluminum oxide sandpaper. If the lathe is not equipped with a non-directional finishing tool, apply the finish with a sanding block and 150-grit aluminum oxide sandpaper. After applying a non-directional finish, clean each friction surface of the brake rotor with denatured alcohol, or an equivalent approved brake cleaner.
  13. Remove the brake rotor from the brake lathe.
  14. Measure the assembled LRO of the brake rotor to ensure optimum performance of the disc brakes. Refer to «Brake Rotor Assembled Lateral Runout Measurement»(ref-277897-S27860650622008012100000) .
  15. If the brake rotor assembled LRO measurement exceeds the specification, bring the LRO to within specifications. Refer to «Brake Rotor Assembled Lateral Runout Correction»(ref-277897-S29626426322008012100000) .

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