Rotor Thickness Variation
Thickness variation in a rotor's braking surface can result in pedal pulsation, chatter and surge. This can also be caused by excessive runout in the rotor or the hub.
Rotor thickness variation measurements should be made in conjunction with measuring runout. Measure thickness of the brake rotor at 12 equal points around the rotor braking surface with a micrometer at a radius approximately 1" (25 mm) from edge of rotor. If thickness measurements vary beyond the specification, the rotor should be re-faced or replaced. See Fig 1.