Rev Up for the 2025 ASE Brakes Certification – Master the Test and Shift Gears to Success!

In a drum brake system, the component that expands to create friction is the brake shoes. When the brake pedal is pressed, hydraulic pressure from the brake fluid pushes the brake shoes outward against the inside surface of the brake drum. This contact generates friction, which slows down or stops the vehicle.

The brake shoes are designed with friction material attached to them, which enhances grip as they are pressed against the drum. The expansion happens because the brake shoes are forced apart by the action of the brake mechanism, which can include elements like the wheel cylinder that translates hydraulic pressure into mechanical movement.

The other components mentioned do not perform the same function. The brake rotor is part of a disc brake system, not a drum brake. The brake caliper holds the brake pads in a disc brake system and is involved in the squeezing action needed to create friction, but it does not expand. Brake lines are conduits that carry brake fluid but do not contribute to friction directly. Understanding the role of each component in a drum brake system is crucial for comprehending how braking works effectively.