Do Rotors Have to Be Turned in a Brake Job?

Many garages will routinely perform a rotor resurfacing with every brake service. An examination of brake service specifications and technical bulletins from auto manufacturers reveals that while rotor resurfacing can be a cost-effective way of addressing minor rotor damage, it need not be performed at every brake servicing.

Rotor Scoring

It is common for ridges and score lines to wear into the brake rotor with time; however, most manufacturers consider that score lines that are less than 0.06 inches in depth need not be addressed by rotor resurfacing.

Disc Thickness Variation

Different areas of the rotor will wear at different rates. Over time, this can mean that higher-wear areas will become thinner than the rest of the rotor. Most manufacturers do not consider that a rotor resurfacing is required unless this thickness variation exceeds 0.001 inches.

Rotor Run-out

The term "run-out" refers to the amount of wobble in the rotor as it turns. This can be due to warpage of the rotor, or to the rotor not being mounted perfectly straight on the hub. Manufacturers generally recommend that a rotor that is not mounted straight on the hub be corrected by shimming of the rotor rather than resurfacing. If the run-out is less than 0.003 inches, resurfacing is not required in any case.

Overall Rotor Thickness

Rotor resurfacing will generally result in the removal of 0.005 to 0.01 inches of material from each side of the rotor. This will reduce the overall rotor thickness by double this amount if each side is resurfaced as it should be. If resurfacing is done at every brake servicing then the rotor life will be shortened.