This SAE 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 document is intended for outboard mounted brake drums and disc wheel hubs used on Class 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 areas.