Modifications of Steering Axle Cam Brakes for FMVSS 121

The increased torque levels required on front axles of air brake vehicles to comply with the 60 miles per hour, 245 foot stopping distance of FMVSS 121 created brake packaging problems not only due to the brake assemblies being larger for a given axle weight, but due to the inclusion of antilock hardware and the larger front axles. To produce the additional torque, increased brake input power was needed, necessitating material and design changes of the basic foundation brake.

Many of these design considerations are discussed in this paper.