What happens to pedal reserve when a brake system is engaged?

When a brake system is engaged and the pedal is depressed, the pedal reserve decreases. Pedal reserve refers to the amount of brake pedal travel that remains after the brake is applied. When the brake pedal is pressed, the hydraulic system of the brake engages and moves the brake components (like calipers or wheel cylinders) into contact with the brake rotors or drums. This movement reduces the available travel left in the pedal since some of it is used to initiate braking action.

As the braking process continues, the distance the driver can still press the pedal is diminished, resulting in a decrease of pedal reserve. In systems where the brakes are functioning correctly, there should still be some reserve to allow for further engagement, but the overall trend is a decrease as pressure builds and the brakes take effect.

Understanding this concept is crucial for inspectors, as a reduction in pedal reserve can indicate potential issues in the braking system that may need attention.