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.. Read More

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 or four answer choices. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the South Dakota Commercial Driver 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. Air tank drains should:

Explanation
Compressed air in an air brake system usually contains a certain amount of water and compressor oil. The water and oil can damage the brakes if left to accumulate in the system. Manually operated air tank drains must be opened daily to remove this build-up.

20. Why do large vehicles use air brakes?

Explanation
If used and maintained properly, air brakes are a safe and effective way to stop large, heavy vehicles.

21. Foundation brakes are used:

Explanation
Foundation brakes are used at each wheel. The most common type is the S-cam drum brake.

22. The air pressure in a dual air brake system should build from 85 to 100 psi within:

Explanation
When inspecting a vehicle with a dual air brake system, you should wait for air pressure to build from 85 to 100 psi in both the primary and secondary systems. This should take about 45 seconds.

23. What kind of brakes do most newer heavy-duty trucks use?

Explanation
Most newer heavy-duty vehicles use dual air brake systems. A dual air brake system has two separate air brake systems which use a single set of brake controls.

24. Air brakes use ____ to function.

Explanation
Air brakes function through the use of compressed air.

25. During an applied leakage test, what is the maximum leakage rate that is safe for a single vehicle with air brakes?

Explanation
It is important to know the maximum air loss rate that is safe for your specific vehicle. A single vehicle with air brakes should have a leakage rate no higher than 3 psi in a minute during an applied leakage test.
DMV Writen Test