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 Missouri Commercial Driver’s 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. During an inspection, slack adjusters on S-cam brakes should not move more than:
Explanation
Check each slack adjuster after parking on level ground, setting wheel chocks, and disengaging the parking brake. Pull the slack adjusters to make sure they do not move more than about one inch from where the push rod is attached. If they move more than one inch, they may be out of adjustment and will need to be fixed.
20. The air compressor is connected to the:
Explanation
The air compressor of an air brake system is connected to the engine through gears or a v-belt. The compressor may be air-cooled or cooled by the engine cooling system.
21. An application pressure gauge shows:
Explanation
If a vehicle is equipped, an application pressure gauge shows how much air pressure is being applied to the brakes. This gauge can help a driver identify if their brakes are beginning to fade.
22. Using an Anti-Lock Braking System (ABS):
Explanation
An Anti-Lock Braking System (ABS) helps to provide additional control during hard braking, but does not necessarily shorten a vehicle's stopping distance.
23. A low air pressure warning signal:
Explanation
Any vehicle with air brakes must be equipped with a low air pressure warning signal.
24. Failing to drain air tanks could result in:
Explanation
In an air brake system, the air tanks must be periodically drained to remove accumulations of water and compressor oil. If water is not removed, it could freeze in cold weather and cause brake failure.
25. If using spring brakes when hauling a heavy load, a complete stop will:
Explanation
