What are the minimum thickness specs for a front brake rotor?

Brake rotor thickness requirements vary by vehicle make, model and year, but the minimum allowable thickness is always cast on an unmachined surface, or alternate part, of the rotor. A technician must remove the wheel and use a micrometer on the rotor to measure its thickness accurately.

The technician must remove any foreign material buildup from the rotor before taking a measurement. The micrometer needs to be 0.4 inch inside of the outer rotor circumference to obtain the correct measurement. The technician takes subsequent readings every 45 degrees, or one-eighth turn, of rotation around the entire rotor to allow for inconsistent wear. When refinishing a rotor, a correct rotor runout reading is also necessary to calculate its minimum necessary thickness.