Whenever the disc
Brake Pads are inspected for wear, it is important to also check the condition of the disc (rotor) surfaces. Light scoring or grooving is normal, but deep grooves or severe erosion are not acceptable. Models from 1974 and earlier feature a single deep groove known as a 'squeal' groove, which should not be mistaken for damage. If vibration occurs during brake pedal application, disc runout may be the cause. To check for this, a dial gauge or feeler blades can be used between the disc and a fixed point, ensuring that the runout does not exceed 0.004 inches. Variations in disc thickness greater than 0.0005 inches can also lead to vibration during braking. Discs typically have wear limit and refinish thickness dimensions cast into them, and if a dealer cannot refinish a disc to meet specified tolerances, a new disc must be installed. When a brake drum is removed for lining inspection, it should be checked for cracks, scoring, or being out of round. An out-of-round drum can cause a pulsating feeling in the brake pedal during application, and the internal diameter should be measured at various points using an internal micrometer. Drums can be refinished internally as long as the wear and refinish sizes cast into them are not exceeded.