Applying the brakes causes the rear brake cylinder piston to force the leading edge of the primary shoe to contact the rotating drum. The shoe tries to rotate with the drum and transfers force to the secondary shoe thorough he rear brake shoe adjuster. The secondary shoe's leading edge bites into the drum and tries to rotate, just like the primary shoe. Since the shoes cannot rotate, they wedge themselves into the drum. The rotating torque from the shoes increases the braking force applied by the rear brake cylinder. Because of this wedging action, the design is a duo-servo, as opposed to a single-servo design where the rear brake cylinder pressure alone is the source of braking force.

The torque from the rear brake shoes is transferred through the rear brake backing plate to the axle flange. Brake adjustments are automatic and occur during reverse brake applications.