Arizona Air Brakes CDL Practice Test

What function does the brake pedal serve in an air brake system?

1. Is used as a footrest during normal driving

2. Controls the speed of the air compressor

3. Controls the air pressure applied to put on the brakes

4. Is connected to slack adjusters by a series of rods and linkages

The correct answer is: Controls the air pressure applied to put on the brakes

The brake pedal in an air brake system plays a crucial role in controlling the application of brakes by directly managing the air pressure that is applied to the brake chambers. When the driver presses the brake pedal, it acts as a signal to the air brake system to release compressed air to the brake chambers, which then activates the brake shoes against the brake drum. This process enables the vehicle to slow down or stop. Understanding this function highlights the pedal's significance; it is not merely for resting the foot, nor does it influence the air compressor's operation. Furthermore, while slack adjusters do play a role in adjusting brake shoe distance, they are not directly controlled by the brake pedal itself. Thus, the primary purpose of the brake pedal is to modulate the air pressure that applies the brakes, ensuring effective and responsive braking action.