A rotor is part of which braking system?

The rotor is a critical component of disc brakes, which is why the choice is correct. In a disc brake system, the rotor is a flat, circular metal disc that is mounted on the wheel's axle. When the brake pedal is applied, brake calipers press friction pads against the rotor, creating the necessary friction to slow down or stop the vehicle. This design allows for better heat dissipation compared to drum brakes, resulting in improved performance and reduced brake fade.

In contrast, while other braking systems like drum brakes and air brakes utilize different mechanisms, they do not feature a rotor. Drum brakes have a drum that houses the brake shoes, while air brakes use a system that primarily relies on compressed air to activate the braking mechanism without a rotor. Hydraulic brakes also rely on fluid pressure to engage brake shoes or calipers, but they don’t involve a rotor as a distinct component like in disc brakes.