Brake roughness is a shudder, vibration or pedal pulsation occurring during braking operation. It may be caused by a foreign materiall build-up on the rotor braking surfaces or by excessive rotor variation or distortion.
If there is a foreign material build-up or contamination found on the rotor or lining surfaces, hand sand both the linings and rotor braking surfaces. Brake squeal or squeak is a higher frequency vibration which can result from foreign material build-up or glazing of the lining and rotor surfaces. Hand sanding the rotor and linings may correct the condition.
Always replace the linings if they are excessively worn. Check the caliper piston for roll back release. A sticking caliper piston can cause rapid lining wear and possible rotor damage. Check the sliding motion of the caliper on the mounting pinrails. Service as necessary.
| Fig. 1: Use a dial indicator to check rotor runout
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Rotors should be replaced for structural damage to the hub casting, for excessive rotor wear when the minimum rotor thickness is below spec, and for heavy scoring or excessive runout.
Lathe turn the rotor to remove minor rotor scoring or scratching that cannot be removed by hand sanding. Deep scoring usually occurs when the lining is worn down to the point where the rivets or metal pad backing contacts the rotor.
Minor rotor runout may be corrected by lathe turning. To check rotor runout, first eliminate wheel bearing end play by correctly adjusting the wheel bearing. Clamp a dial indicator to the steering knuckle assembly so that the stylus contacts the rotor about one inch from the outer edge. Rotate the rotor and take an indicator reading. If the reading exceeds 0.008–0.010 inch total lateral runout within a six-inch radius, replace or resurface the rotor.
