Air Brakes
This endorsement is required for driving a vehicle with air brakes. To receive this endorsement, applicants must pass a written test. The test consists of 25 multiple choice questions. Each question has three answer choices. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the Idaho Commercial Driver’s License Manual. Questions come from the chapter covering: Air Brakes. The Air Brakes endorsement may be used with the Class A, B or C CDL.
Number of Question
Passing Score
19. When you press the brake pedal in a vehicle with S-cam brakes, air pressure pushes out the rod and moves the:
Explanation
When pressing the brake pedal in a vehicle with S-cam brakes, air will enter the brake chambers. The added air pressure will push out the rods and move slack adjusters, twisting the brake camshafts.
20. Before driving a vehicle with a dual air brake system, you must wait for the air compressor to build a minimum of ____ in both the primary and secondary systems.
Explanation
Before driving a vehicle with a dual air brake system, you should wait for the air compressor to build up at least 100 psi in both the primary and secondary systems.
21. The leakage rate for a triple combination vehicle with air brakes should be no more than ____ in one minute during a static leakage test.
Explanation
When performing a static leakage test on a triple combination vehicle with air brakes, the leakage rate should be no more than 5 psi in one minute. If the air leaks from the air brake system at a quicker rate, the vehicle should not be driven because something likely needs to be repaired.
22. Air brakes use ____ to function.
Explanation
Air brakes function through the use of compressed air.
23. Which of the following is not a part of an air brake system?
Explanation
Air brakes consists of three separate braking systems: the service brake system, the parking brake system, and the emergency brake system.
24. In a vehicle with dual parking control valves, once air pressure is lost and the spring brakes come on:
Explanation
In a vehicle with dual parking control valves, there is a separate air tank that can be used to temporarily release the spring brakes if they have been activated due to low air pressure. Pushing in the proper control will release the spring brakes for a short period of time, allowing the driver to move the vehicle in an emergency.
25. ____ make up the emergency brake system.
Explanation
