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Disc Brake System: Other Cadillac STS I

Mechanical - Hydraulic ~1432 words

Brake Rotor Thickness Measurement

CAUTIONRefer to Brake Dust Caution in Cautions and Notices.
  1. If the inboard friction surface of the brake rotor is not accessible, reposition and support the caliper with the brake pads. Refer to «Brake Pads Replacement - Front (JE5)»(ref-197582-S42046762352005101200000) or «Brake Pads Replacement - Front (JL9)»(ref-197582-S32028247102005101200000) or «Brake Pads Replacement - Front (J56)»(ref-197582-S17747266772005101200000) and/or «Brake Pads Replacement - Rear (JL9, JE5)»(ref-197582-S22519736202005101200000) or «Brake Pads Replacement - Rear (J56)»(ref-197582-S34837821402005101200000) .
  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. Compare the lowest thickness measurement recorded to the following specifications: Specification: Front brake rotor minimum allowable thickness after refinishing: 30.7 mm (1.209 in) Front brake rotor (J56) minimum allowable thickness after refinishing: 31.0 mm (1.220 in) Rear brake rotor minimum allowable thickness after refinishing: 24.0 mm (0.944 in) Front brake rotor discard thickness: 30.7 mm (1.209 in) Front brake rotor (J56) discard thickness: 30.00 mm (1.181 in) Rear brake rotor discard thickness: 24.0 mm (0.944 in) Rear brake rotor (J56) minimum allowable thickness after refinishing: 27.0 mm (1.062 in) Rear brake rotor (J56) discard thickness: 26.00 mm (1.023 in)
  5. 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.
  6. 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.
  7. 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 in Cautions and Notices.
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 «Brake Pads Replacement - Front (JE5)»(ref-197582-S42046762352005101200000) or «Brake Pads Replacement - Front (JL9)»(ref-197582-S32028247102005101200000) or «Brake Pads Replacement - Front (J56)»(ref-197582-S17747266772005101200000) and/or «Brake Pads Replacement - Rear (JL9, JE5)»(ref-197582-S22519736202005101200000) or «Brake Pads Replacement - Rear (J56)»(ref-197582-S34837821402005101200000) .
  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: 0.02 mm (0.001 in)
  6. If the brake rotor thickness variation measurement exceeds the specification, the rotor requires refinishing or replacement.

Burnishing Pads and Rotors

CAUTIONRoad test a vehicle under safe conditions and while obeying all traffic laws. Do not attempt any maneuvers that could jeopardize vehicle control. Failure to adhere to these precautions could lead to serious personal injury and vehicle damage.
CAUTIONRefer to Brake Dust Caution in Cautions and Notices.

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.

Tools Required

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

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

CAUTIONRefer to Brake Dust Caution in Cautions and Notices.
IMPORTANTBrake 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 . 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). Refer to Brake Rotor Assembled Lateral Runout (LRO) Measurement .
  1. Ensure that the caliper and caliper bracket that are already being supported, are clear from contacting any rotating components, such as the brake rotor.
  2. Remove the J 45101-100 and the lug nuts that were installed during the assembled LRO measurement procedure and/or the indexing correction procedure. See «Special Tools»(ref-197582-S10500389362005101200000) .
  3. Inspect the mounting surface of the hub/axle flange and the brake rotor to ensure that there are no foreign particles or debris remaining.
  4. Set up the lathe, following the manufacturer's instructions.
  5. Refinish the brake rotor, following the brake lathe manufacturer's instructions.
  6. After each successive cut, inspect the brake rotor thickness. Refer to «Brake Rotor Thickness Measurement»(ref-197582-S21297169622005101200000) .
  7. If at any time the brake rotor exceeds the minimum allowable thickness after refinish specification, the brake rotor must be replaced. After replacing the rotor, proceed to step 10.
  8. 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
  9. Remove the lathe from the vehicle.
  10. Measure the assembled LRO of the brake rotor. Refer to «Brake Rotor Assembled Lateral Runout (LRO) Measurement»(ref-197582-S09289980392005101200000) .
  11. If the brake rotor assembled LRO measurement still exceeds the maximum allowable specification, refer to «Brake Rotor Assembled Lateral Runout (LRO) Correction»(ref-197582-S13433819842005101200000) .
  12. If the brake rotor assembled LRO is within specification, install the brake caliper and depress the brake pedal several times to secure the rotor in place before removing the J 45101-100 and the lug nuts. See «Special Tools»(ref-197582-S10500389362005101200000) .

Brake Rotor Refinishing

Tools Required

  1. J 41013 Rotor Resurfacing Kit. See «Special Tools»(ref-197582-S10500389362005101200000) .
  2. J 42450-A Wheel Hub Resurfacing Kit. See «Special Tools»(ref-197582-S10500389362005101200000) .
CAUTIONRefer to Brake Dust Caution in Cautions and Notices.
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.
  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-197582-S10500389362005101200000) .
  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-197582-S10500389362005101200000) .
  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-197582-S21297169622005101200000) .
  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 lateral runout (LRO) of the brake rotor to ensure optimum performance of the disc brakes. Refer to «Brake Rotor Assembled Lateral Runout (LRO) Measurement»(ref-197582-S09289980392005101200000) .
  15. If the brake rotor assembled LRO measurement exceeds the specification, bring the LRO to within specifications. Refer to «Brake Rotor Assembled Lateral Runout (LRO) Correction»(ref-197582-S13433819842005101200000) .

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