Which component contacts the drum first during forward braking?

The primary shoe is the first component that contacts the drum during forward braking in drum brake systems. This design allows for more effective braking performance because the primary shoe is strategically positioned to take advantage of the direction of rotation of the drum. When the brakes are applied, the primary shoe engages the drum first due to its placement, creating a wedging action that enhances the overall effectiveness of the braking force.

This initial contact helps to stabilize and secure the braking action, preventing the shoes from sliding against the drum, which can reduce efficiency. The secondary shoe usually follows the primary shoe but relies on the movement of the primary shoe pressing it against the drum for additional braking force. Understanding this dynamic is essential for comprehending how drum brake systems operate and the roles of the various components involved.