This recommended practice contains dimensions and tolerances for outboard mounted brake drums and disc wheel hubs in the interface areas. The geometric features described in this document are shown at true position. This recommended practice is intended for outboard mounted brake drums and disc wheel hubs used on Class 7 and 8 commercial vehicles. Included are SAE J 694 mounting systems II, III, XIV, and X. Special and less common applications are not covered.

This recommended practice defines and documents the dimensions and tolerances necessary to maintain interchangeability in the interface areas. Components of different mounting systems with common bolt patterns could be mixed together and cause service problems. Therefore, it is important to note that each mounting system should be treated individually and their components not be intermixed.