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 or four answer choices. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the Alabama 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
13. What kind of force must emergency brakes use?
Explanation
Because air pressure can eventually leak away, the emergency brakes in an air brake system must be held on by mechanical force.
14. Front brake limiting valves were intended to:
Explanation
Some older vehicles with air brakes have front brake limiting valves. These valves were intended to reduce the risk of front wheels skidding. However, research has shown that such devices are unnecessary, so they should be left in the "normal" position.
15. What can happen if a parking brake is used in very wet weather when temperatures are below freezing?
Explanation
If you use the parking brakes when the weather is very wet and the temperature is below freezing, the brakes may become frozen, preventing the vehicle from moving.
16. How many air storage tanks are used in an air brake system?
Explanation
Air storage tanks are used to hold compressed air. The number and size of air tanks in an air brake system varies among vehicles.
17. In a dual air brake system, air pressure should build from 85 to 100 psi within ____ seconds.
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.
18. If the brake pads rub against the brake drums and create too much heat:
Explanation
