Which component of the brake system directly controls the car’s ability to stop?

The component of the brake system that directly controls the car's ability to stop is the brake pads. Brake pads are crucial because they create friction against the brake rotor, which is attached to the wheel. When the brake pedal is pressed, hydraulic pressure is applied from the master cylinder through the brake lines to the brake calipers, which then push the brake pads against the rotor. This friction is what ultimately slows down and stops the vehicle.

In contrast, the master cylinder plays a role in generating the hydraulic pressure necessary for braking but does not directly engage with the wheels. The brake lines are the pathways through which the brake fluid travels, transmitting the pressure from the master cylinder to the brakes, but they do not have a direct role in stopping the car. The brake pedal serves as the driver’s input to initiate braking, but again, it’s the brake pads that perform the actual stopping action by generating the needed friction against the rotational motion of the wheels.