Which component prevents the shoes from rotating with the drum?

The anchor pin is crucial in drum brake systems as it serves a specific function in holding the brake shoes in place. When the brake is applied, the shoes need to press against the drum to create the friction necessary to slow down or stop the vehicle. The anchor pin effectively prevents the shoes from rotating with the drum during this process, allowing them to pivot on the anchor point instead. This ensures that the shoes can expand outward, pressing against the inner surface of the drum, which is essential for effective braking.

In contrast, the other components serve different roles within the braking system. The caliper is involved in disc brakes and not relevant in a context discussing drum brakes. The piston spring helps return the brake shoes to their resting position but does not prevent rotation. The adjusting screw is used to maintain the proper distance between the shoes and the drum but does not serve the purpose of anchoring the shoes during braking. Therefore, the anchor pin is the key component that ensures stability and functionality of the brake shoes.