Which part in the drum brake system expands outward against the drum to stop a vehicle when brakes are applied?

In a drum brake system, the shoes are the components that expand outward against the drum to create friction and stop the vehicle when the brakes are applied. When the driver presses the brake pedal, hydraulic force is transmitted through the brake lines to the wheel cylinders, which then push the brake shoes outward against the inner surface of the brake drum.

The friction created between the shoes and the drum slows down the rotation of the wheel, ultimately bringing the vehicle to a stop. This function is crucial for the braking process, making the brake shoes a key element in drum brake performance. The other components listed play supportive roles: pads are used in disc brakes, bushings provide support and reduce friction in various moving parts, and springs are used to retract the brake shoes back into their original position once the brakes are released. This clarifies why the shoes are the correct answer for the part that directly engages with the drum to halt the vehicle.