GM Grand Am/Achieva/Calais/Skylark/Somerset 1985-98

Brake Disc (Rotor)

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REMOVAL & INSTALLATION



See Figure 1

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Fig. Fig. 1: Removing the rotor from the hub

  1. Raise and safely support the vehicle.
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  3. Remove the tire and wheel assembly.
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  5. Unfasten the caliper mounting bolts, then carefully remove the caliper (along with the brake pads) from the rotor. Do not disconnect the brake line; instead, wire the caliper out of the way with the line still connected.
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  7. Remove the rotor by simply pulling it off of the hub and bearing assembly.
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  9. The installation is the reverse of the removal procedure.
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INSPECTION



Check the disc brake rotor for scoring, cracks or other damage. Rotor run-out should be measured while the rotor is installed, while rotor thickness/thickness variation may be checked with the rotor installed or removed. Use a dial gauge to check rotor run-out. Check the rotor thickness to make sure it is greater than minimum thickness and check for thickness variations using a caliper micrometer.

Thickness Variation See Figure 2

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Fig. Fig. 2: Check brake rotor thickness in several places around the rotor

  1. Measure the thickness at four or more points on the rotor. Make all measure measurements at the same distance in from the edge of the rotor. Use a micrometer calibrated in ten-thousandths of an inch.
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  3. A rotor that varies in thickness by more than 0.0005 in. (0.013mm) can cause pedal pulsation and/or front end vibration during brake applications. A rotor that does not meet these specifications should be resurfaced to specifications or replaced.
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Lateral Run-out See Figure 3

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Fig. Fig. 3: Use the lug nuts to secure the rotor to the hub when checking rotor run-out

  1. Remove the wheel and tire assembly.
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  3. Fasten the lug nuts to retain the rotor.
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  5. Secure a dial indicator to the steering knuckle so the indicator button contacts the rotor at about 0.5 in. (13mm) from the outer edge of the rotor.
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  7. Set the dial indicator to zero.
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  9. Turn the wheel one complete revolution and observe the total indicated run-out.
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  11. If the run-out exceeds 0.0031 in. (0.08mm), resurface or replace the rotor.
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