Air Brakes
This endorsement is required for driving a vehicle with air brakes. To receive this endorsement, applicants must pass a test. The test consists of 25 multiple choice questions. Each question has four answer choices. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the Texas Commercial Motor Vehicle Drivers Handbook. Questions come from chapters covering: Air Brakes. The Air Brakes endorsement may be used with the Class A, B or C CDL.
Number of Question
Passing Score
19. Before a vehicle with dual air brakes is driven, pressure of at least ____ should be built up in both braking systems.
Explanation
Before driving a vehicle with a dual air brake system, allow time for the air compressor to build up pressure of at least 100 psi in both the primary and secondary systems.
20. To ensure normal stopping power, drivers of vehicles equipped with a front brake limiting valve should:
Explanation
Some pre-1975 vehicles have a front brake limiting valve, which has "normal" and "slippery" settings. The idea behind these valves was to limit the air pressure available to the front brakes when driving on slippery surfaces, and thereby reduce the danger of a front-wheel skid. Studies have found that this is not actually a concern, so if your vehicle has a front brake limiting valve, leave it in the "normal" position.
21. While driving, spring brakes are generally held in place by:
Explanation
While driving, spring brakes are generally held in place by air pressure. If the air pressure gets low enough, the springs will activate the brakes.
22. When the brake pedal is pushed down, air brakes work:
Explanation
Because air takes time to flow through the air lines to the brakes, air brakes cannot begin working instantly. There is often a brake lag of at least one-half of a second between the moment the brake pedal is pressed and the moment the brakes begin to work.
23. 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.
24. The air storage tanks:
Explanation
In an air brake system, the air storage tanks hold enough air for brakes to be used several times if the compressor stops working.
25. When using the controlled braking method in an emergency situation, you should:
Explanation
