CTS 2003-2005

Brake Disc (Rotor)

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Inspection



It should not be necessary to refinish the brake rotors when performing routine brake maintenance such as replacing worn disc brake pads. Refinish a rotor only if a pulsation is felt in the brake pedal and/or there is a scoring of the rotor greater than 0.060 inch (1.5 mm).

All brake rotors have a minimum thickness dimension number cast into them. This dimension is the minimum wear dimension and not a refinish dimension. Do not use a brake rotor that, after refinishing, will not meet the specification shown on the rotor. Always replace it with a new rotor.


NOTE
It is extremely important that a brake rotor have very little lateral runout. It must turn true or the rotor will wobble on the wheel hub. This wobble will force the brake caliper piston to rapidly pulse in and out of the caliper. This results in a pulsating feel to the brake pedal when applied. Whenever a rotor has been separated from the wheel bearing flange, clean any rust or contaminants from the wheel flange and brake rotor mating surfaces. Even relatively small particles of dirt, rust or other foreign material between the face of the wheel hub and the back face of the brake rotor is enough to cause problems. Failure to keep the metal contact mating surfaces clean may result in increased lateral runout of the rotor and brake pulsation.



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Fig. A rotor with grooved this deep will have to resurfaced or, more likely, replaced

Thickness Variation

The thickness variation can be checked by measuring the thickness of the rotor at four or more points. All of the measurements must be made at the same distance from the edge of the rotor. GM recommends using a micrometer that reads in ten-thousandths of an inch. They feel rotor condition is that critical. A rotor the varies by more than 0.005 inch (0.013 mm) can cause a pulsation in the brake pedal. If these measurement are excessive, the rotor should be refinished or replaced.

Removal & Installation





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Fig. The rotor is removed by sliding it straight off the lug studs

  1. Using a suction gun, remove approximately 2 / 3 of the brake fluid from the master cylinder. The reason for this is that the caliper pistons must be pushed back into their bores so the caliper can be removed from the rotor. This could cause the brake fluid to overflow from the reservoir onto painted surfaces or wiring.
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  3. Raise and safely support the vehicle on safety stands.
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  5. Mark the relationship of the wheel to the hub so it can later be installed in the same relationship. This helps retain the balance of the rotating assembly.
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  7. Remove the tire and wheel assembly.
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  9. It is not necessary to remove the brake lines or parking brake cable (as equipped) when removing a caliper to service the brake rotors. It is necessary to use care not to damage the brake hose by letting the caliper hang. The weight of the caliper can damage the brake hose. Remove the caliper using the procedures found in this section and suspend it from the strut with a wire hook or suitable piece of wire. Do NOT disconnect the brake hose or allow the caliper to hang from the brake line.
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  11. Remove the rotor assembly by simply pulling it off the hub.
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To install:

  1. Clean all parts well. Make sure the metal contact surfaces between the brake rotor and the hub bearing flange are clean. Sandpaper and/or wirebrush these areas to make sure they are clean.
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  3. Install the brake rotor over the hub assembly.
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  5. Install the brake caliper as outlined in this section.
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  7. Install the wheel and tire assembly.
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  9. Carefully lower the vehicle, then fill the master cylinder reservoir to the FULL level with the correct type of DOT 3 brake fluid from a clean, unsealed container.
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  11. Firmly depress the brake pedal three times before moving the vehicle. This reseats the brake pads and moves the caliper pistons back to their operating positions. Do not attempt to move the vehicle until a firm brake pedal has been established.
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