Run‐Out = Steering Wheel Vibration
A rotor with lateral run‐out will not wear evenly, and problems will emerge over time. As the vehicle travels down the road with the brakes relaxed (off), the rotor will brush each pad once per revolution. This will result in a thin spot on the rotor ‐ disc thickness variation or DTV.
Also check that the rotor does not have a run‐out problem due to rust build up between the disc mount surface and the hub.
Not all pedal pulsation is due to discs with DTV. One potential cause is brake pad material operating outside of its designed temperature range; it may have left a thick (as in “thicker than normal”) deposit in one area of the disc surface, creating a “sticky” spot that will grab with every revolution of the disc. Grease or other foreign materials (usually deposited on the disc during wheel maintenance) can likewise create a slippery spot on the disc, also creating the sensation of a grab or brake disc with DTV.
Typical DBA Rotor Specifications for Passenger Cars Thickness variation targets for DBA rotors: less than 0.010mm / 0.0004” Lateral runout targets for DBA rotors: less than 0.050mm / 0.002” (about the thickness of a human hair).
Disc Brakes Australia