The purpose of this Recommended Practice is to identify and define the significant factors required for assembly process control.The proper assembly of wheels on trailers is of critical importance to consumer safety. The improper attachment of a wheel to an axle may lead to the loss of the wheel in service. This loss can lead to highway safety risks from flying debris or the loss of control of the trailer and/or towing vehicle. The careful design of the wheel assembly process and systematic control of that process will improve trailer reliability and enhance consumer safety.