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. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the Michigan 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. What tells you how much pressure is in your vehicle's air tanks?

Explanation
A vehicle that is equipped with air brakes must also be equipped with a supply pressure gauge. This gauge tells the driver how much air pressure is in each of the vehicle's air tanks.

8. On flat surfaces, wheel chocks:

Explanation
In situations where a driver cannot use a parking brake, wheel chocks can be used to hold a parked vehicle in place on a level surface.

9. Before driving a vehicle with air brakes, you should ensure that the ____ come on automatically when air pressure falls below 45 psi.

Explanation
Before driving a vehicle with air brakes, you should ensure that the spring brakes come on automatically when air tank pressure falls to a level between 20 and 45 psi. You can do this by chocking the wheels and releasing air from the braking system by stepping on and off the brake pedal. Once the pressure levels drop to an unsafe level, the parking brake valve should pop out and spring brakes should come on.

10. Air tank drains:

Explanation
Compressed air in an air brake system usually has a certain amount of water and oil in it. This can harm the system if allowed to accumulate. Air tanks have drain valves to aid in removing water and oil from the compressed air.

11. What can happen if the air pressure gets too low in an air brake system?

Explanation
Pressing and releasing the brake pedal unnecessarily can let air out of the braking system faster than the compressor can replace it. Air brakes may cease to work effectively if the pressure becomes too low.

12. Once the air tanks are at an air pressure level of 125 psi, the air compressor governor will:

Explanation
An air compressor governor will stop the compressor from pumping air once the air tanks are at an air pressure level around 125 psi. This air pressure level is referred to as the "cut-out" level.
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