Instructions

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 Illinois Commercial Driver’s License Study Guide. 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 25

Passing Score 20

19. Foundation brakes are used:

Only at the front wheels.

Only at the rear wheels.

Only at the driver’s side wheels.

At each wheel.

Foundation brakes are used at each wheel. The most common type is the S-cam drum brake.

20. The air storage tanks:

Hold only enough air for one braking cycle.

Hold enough air for brakes to be used several times if the compressor stops working.

Do not hold air unless there is an emergency.

Hold enough air for more than 1,000 braking cycles.

In an air brake system, the air storage tanks hold enough air for brakes to be used several times if the compressor stops working.

21. A dual air brake system:

Has a single air brake system, but uses two sets of controls.

Has one air brake system for each side of the truck.

Has two brakes for each wheel.

Has two separate air brake systems, but uses a single set of controls.

A dual air brake system has two separate air brake systems that use a single set of brake controls. One system typically operates the regular brakes on the rear axle or axles. The other system operates the regular brakes on the front axle.

22. If braking at a speed of 55 mph while driving on dry pavement, the brake lag can add ____ to your vehicle's total stopping distance.

32 feet

15 feet

50 feet

10 feet

The total stopping distance for vehicles equipped with air brakes is made up of four factors: perception distance, reaction distance, brake lag distance, and braking distance. When braking at a speed of 55 mph while driving on dry pavement, the brake lag can add around 32 feet to a vehicle's total stopping distance.

23. To use the stab braking method, you should:

Apply the brakes completely until the wheels lock up, release the brakes until the wheels start rolling, then repeat the process.

Apply the brakes about halfway, but allow the wheels to keep rolling.

Apply the brakes completely until the wheels lock up and the vehicle stops.

Apply the emergency brake until the vehicle starts to slow.

The stab braking method for emergency stops involves fully applying the brakes until they lock up. The brakes are then released until the wheels start rolling, and then the process is repeated.

24. Brake fading is caused when:

Brakes are not used often enough.

Brakes overheat.

Brakes are too cold.

Brakes are wet.

Using the brakes excessively will cause them to overheat, making them less effective. This is referred to as "fading."

25. If using air tanks with manually operated drains, how often should you drain the tanks?

Every day

Once a week

Once a month

Once every 3,000 miles

To prevent the build up of oil and water in a vehicle's air tanks, manually operated air tank drains should be used at the end of each day of driving.

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