What component contacts the drum first during forward braking?

The primary shoe is the component that contacts the drum first during forward braking in a drum brake system. When the brake pedal is applied, hydraulic pressure pushes the wheel cylinder, causing the primary shoe to pivot and press against the brake drum. This initial contact is crucial for effective braking as it begins the deceleration of the vehicle.

The design of the braking system incorporates the primary shoe, which is typically positioned in a manner that allows it to engage with the drum first. After the primary shoe makes contact, the secondary shoe will follow, further enhancing the braking force. This staggered action helps distribute the braking force more evenly and efficiently, allowing for effective stopping power while also minimizing the risk of brake lock-up.

Moreover, the adjustment features and other components like the adjusting screw and drum cylinder play supportive roles in the operation of the brake system, but they do not directly initiate contact with the drum during the braking process. Understanding this interaction helps in diagnosing braking issues and ensuring the effective maintenance of brake systems.