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. Each question has two, three or four answer choices. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the South Carolina 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 25

Passing Score 20

13. Using the brakes creates heat. If too much heat is produced:

The brakes may not work.

The brakes may squeak more than usual.

The brakes will brake unevenly.

Brakes are designed to take a lot of heat, but drivers should not rely solely on the brakes to slow their vehicle. Brakes may fade and lose their ability to slow down the vehicle if they become too hot, so drivers should also rely on the engine braking effect.

14. What do the two systems of a dual air brake system share?

Hoses

An air compressor

Air tanks

Both systems in a dual air brake systems share a single air compressor. If the air compressor is damaged, neither system will be able to operate properly.

15. What do air brakes use to make the brakes work?

Compressed air

Outside air

Non-compressed air

Many large CMVs are equipped with air brakes. An air braking system uses compressed air to operate.

16. During a walk-around inspection, ensure there are no cracks on the brake drums that are more than ____ of the width of the friction area.

One half

One quarter

One third

One tenth

Before beginning a trip, it is important to check the brake drums during your walk-around inspection. It is unsafe to drive if any brake drum has a crack more than one half of the width of the friction area.

17. Why do you need to drain air tanks regularly?

Because the air gets old and needs to be replaced

Because compressed air contains some water which must be drained from the tanks

To allow for a change in air pressure

To remove bad air from the tanks

Compressed air in an air brake system usually contains a certain amount of water and compressor oil. The water and oil can damage the brakes if left to accumulate in the system. Tanks must be drained regularly to remove this build-up.

18. The most common type of foundation brake used is the:

S-cam drum brake.

C-cam drum brake.

G-cam disc brake.

P-cam disc brake.

The most common type of foundation brake is an s-cam drum brake.

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