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 two, three or four answer choices. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the South Carolina 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

1. Brakes out of adjustment will:

Explanation
Brakes out of adjustment will fade before those that are properly adjusted. Brake adjustment must be checked frequently to help prevent brake issues.

2. Air brakes are:

Explanation
As long as the brakes are properly maintained, using air brakes is a safe and effective method of stopping large, heavy vehicles.

3. During an applied leakage test, the maximum leakage rate for a triple combination vehicle is:

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.

4. Friction in an S-cam brake is caused when the brake shoes and linings:

Explanation
Friction inside a brake drum is caused when the brake shoes and linings push against the inside of the drum. The friction in the drums will slow and stop the vehicle.

5. Brakes may get out of adjustment:

Explanation
Brakes can get out of adjustment quickly, especially if they are used to the point of overheating. Brake adjustment should be checked frequently.

6. How is water and compressor oil removed from the bottom of an air storage tank?

Explanation
Water and compressor oil are removed from air storage tanks through a drain valve. The water and oil can damage the brakes if left to accumulate in the system. Manually operated tanks must be drained every day to remove this build-up.
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