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

7. To inspect slack adjusters on S-cam brakes, you need to:

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.

8. When experiencing cold weather, be sure to check your vehicle's alcohol evaporator:

Explanation
An alcohol evaporator can help prevent ice from building up in an air brake system. In cold weather, the evaporator should be checked and refilled every day.

9. If the spring brakes are on, you should:

Explanation
You should not apply the brake pedal if the spring brakes are activated. The brakes could be damaged if they are subjected to the force of air pressure and the springs at the same time.

10. A modulating control valve can control the:

Explanation
A modulating control valve allows a driver to gradually apply spring brakes. In equipped vehicles, the valve is controlled by a lever located on the dashboard.

11. During an applied leakage test, the maximum leakage rate for a triple combination vehicle is ____ in a minute.

Explanation
It is important to know the maximum air loss rate that is safe for your specific vehicle. A triple combination should have a leakage rate no higher than 6 psi in a minute during an applied leakage test.

12. Foundation brakes are used:

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