Michigan State Brakes Certification Practice Exam

In a single anchor duo-servo drum brake system, which shoe does most of the braking?

1. Primary shoe

2. Secondary shoe

3. Leading shoe

4. Tensioning shoe

The correct answer is: Secondary shoe

In a single anchor duo-servo drum brake system, the secondary shoe is primarily responsible for most of the braking. This configuration features two shoes—the primary and secondary—attached at a common anchor point. When the brakes are applied, the leading edge of the primary shoe makes contact with the drum in a direction that assists in the braking action. Meanwhile, the secondary shoe, which is positioned in a way to lead the braking process, effectively takes on a larger share of the force exerted against the drum. This is due to the design of the system; as the drum rotates, the motion effectively tightens the secondary shoe against the drum, increasing the friction and braking force. As a result, the secondary shoe becomes the dominant force in slowing down the vehicle. Understanding this mechanism is crucial for grasping how different components of drum brake systems work in tandem to provide effective stopping power.