Parallelism

DESCRIPTION
Parallelism is the variation in the thickness of the disc brake rotor. If the two rubbing surfaces of the disc brake rotor are not parallel, the disc brake rotor may cause excessive brake pedal travel, a pulsating brake pedal or noise.

METHODS OF TESTING
Two methods can be used to check if the two faces of a disc brake rotor are parallel.

Measuring Thickness Of Disc Brake Rotor Braking Surface:

Method 1 - Using a hand held micrometer.
^ A micrometer can be used to measure the disc brake rotor thickness at 12 points approximately 30° apart and 25.4 mm (1 inch) from the outer edge of the disc brake rotor.

Method 2 - Using a percision lathe.
^ Attach two Rotunda Disc Rotor and Ball Joint Gauges or equivalent, one on each side of the disc brake rotor, so the stylus of each indicator contacts the rubbing surface, directly opposite each other, approximately 10 mm (3/8 inch) from the outer edge of the disc brake rotor.
^ Zero both indicators and rotate the disc brake rotor by hand, while watching both dials. If the total readings of both indicators exceeds specification, the disc brake rotor must be refinished or replaced.

SPECIFICATIONS
Thickness Variation, Maximum:
Front:
15 inch Wheels: 0.010 mm (0.00039 inch)
16 inch Wheels: 0.009 mm (0.00035 inch)
Rear:
All Wheels: 0.010 mm (0.00039 inch)