This SAE Recommended Practice defines wheel mounting systems and documents, the dimensions and tolerances necessary to maintain serviceability, and interchangeability in the interface areas. To be consistent with ISO, it is divided into two sections (I & II). Section I is in concert with ISO 4107, describing mounting systems currently used internationally and nominated for, or included in, the international standards for bolt circle interfaces. Section II records information on current mounting systems also used in North America. Components of different mounting systems with common bolt patterns could be mis-assembled 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.