The drum brake assembly is a duo-servo design. The force applied by the wheel cylinder to the primary shoe forces the leading edge of the shoe to contact the rotating drum.

The shoe tries to rotate with the drum and transfers force to the secondary shoe through the star-wheel 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 increases the braking force applied by the wheel cylinder. Because of this wedging action, the design is a duo-servo as opposed to a single-servo design where the wheel cylinder pressure alone is the source of the braking force.

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