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 answer choices. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the Missouri Commercial Driver’s 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. Air brakes use ____ to function.
Explanation
Air brakes function through the use of compressed air.
2. The two markings on a front brake limiting valve usually read:
Explanation
Some vehicles with air brake systems manufactured before 1975 have a front brake limiting valve with "normal" and "slippery" settings.
3. A slack adjuster should move no more than ____ from where it is attached to the push rod.
Explanation
Before a trip, you should check each slack adjuster after parking, setting wheel chocks, and disengaging the parking brake. Pull the slack adjusters to make sure that 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.
4. 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.
5. When parking, you should not use the parking brake if:
Explanation
If your brakes are hot after coming down a steep grade, you should not use your parking brake when parking. Let your brakes cool before applying the parking brake or risk damaging the brakes.
6. The leakage rate for a triple combination vehicle with air brakes should be no more than ____ in one minute during a static leakage test.
Explanation
