Rotor Parallelism

If the road test has established a front brake shudder condition, the following procedure should be used to isolate the cause:
1. Remove the lug nuts. Before removing the wheel, mark the wheel and one of the lug bolts so that the wheel can be installed in its original position.
2. Examine the condition of the front disc brake rotor and brake pads and linings. If there is visible evidence of lining deposits or light corrosion on the front disc brake rotor, this should be removed using emery paper and a flat block.
3. Measure the thickness of the front disc brake rotor using a suitable micrometer. The standard rotor thickness for a new front disc brake rotor is 26 mm (1.02 inch). The minimum front disc brake rotor thickness is 24.75 mm (0.974 inch). If the front disc brake rotor thickness is less than 24.75mm (0.974 inch), replace the front disc brake rotor.





4. Check the parallelism (thickness variation) of the front disc brake rotor using a suitable micrometer. Measure the front disc brake rotor at eight positions 45 degrees apart about 13 mm (1/2 inch) in from the outside diameter. If any of these readings vary by 0.01 mm (0.0004 inch) or more, the front disc brake rotor should be reconditioned or new front disc brake rotors should be installed.

NOTE: It is important to always check the parallelism (thickness variation) at a constant radius.

5. Install wheel and tire assembly, using Rotunda Accutorq(r). Lug Nut Sockets 164-R0303 or equivalent on 1/2 inch drive air impact wrench or torque wrench to tighten lug nuts to 115-142 Nm (85-105 ft. lbs.).

CAUTION: Failure to tighten lug nuts in a star pattern may result In high rotor runout, which will speed up the development of brake roughness, shudder and vibration.

6. Road test to confirm repair.

If a concern remains, use the Symptom Chart in order to isolate it to a specific subsystem and condition description. From this description a list of possible sources can be used to further narrow the cause to a specific component or condition.