This SAE Recommended Practice establishes dimensions and tolerances for the interface between inboard mounted disc brake rotors and disc wheel hubs. The geometric features described in this document are shown at true position. This document is intended for inboard mounted disc brake rotors and disc wheel hubs for Class 5, 6, 7, and 8 commercial vehicles. Special and less common applications are not covered. This document defines and documents the dimensions and tolerances necessary to maintain interchangeability in the interface of disc brake rotors and hubs. It is intended to provide direction for future designs and aid in industry standardization. This document uses the practice of defining hub and rotor mounting systems. Components of different mounting systems, but with common bolt patterns could be mis-assembled and cause service problems. Therefore, it is important to note that each mounting system should be treated individually and their components not be intermixed. It should also be noted that images shown are typical of the various hub and rotor systems. However, other variants may exist.