In a drum brake system, the S-cam's role is to push the brake shoes outward against the drum.

In a drum brake system, the S-cam's role is to push the brake shoes outward against the drum.

• A. To push the brake shoes outward against the drum
• B. To pull the wheel to the side
• C. To adjust the drum speed
• D. To seal the brake chamber

Answer: (A)

The S-cam in a drum brake converts the push from the brake chamber into outward motion of the brake shoes. When air pressure moves the push rod, the S-shaped cam rotates and its lobes push the two shoes apart, forcing them to press against the inside of the drum. This contact creates friction to slow the wheel. It isn’t responsible for pulling the wheel to one side, adjusting drum speed, or sealing the brake chamber—those are other functions in the system.

The S-cam in a drum brake converts the push from the brake chamber into outward motion of the brake shoes. When air pressure moves the push rod, the S-shaped cam rotates and its lobes push the two shoes apart, forcing them to press against the inside of the drum. This contact creates friction to slow the wheel. It isn’t responsible for pulling the wheel to one side, adjusting drum speed, or sealing the brake chamber—those are other functions in the system.