Operation Redesign: Axles and Brakes for MVSS 121

The purpose of this paper is to discuss the detail known to affect the design of axles, brakes, wheels, and related equipment that will be used on air-braked vehicles under Federal Motor Vehicle Safety Standard (FMVSS) 121. In specific, this paper shows the change that is expected to occur on redesigned axle and braking equipment compatible with the higher levels of vehicle deceleration and controllability to satisfy the Standard.

Variables affecting vehicle brake performance and design and application problems related to MVSS 121 qualification are presented.