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 three answer choices. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the Virginia 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

1. While driving, ____ generally holds spring brakes in place.

Air pressure

Electricity

Gasoline

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.

2. Anti-Lock Braking Systems (ABS):

Reduce a vehicle's normal braking capacity.

Are in addition to other braking systems and do not reduce a vehicle's braking power.

Are not effective on larger vehicles.

If equipped, ABS is in addition to a vehicle's normal braking system and does not increase or decrease the braking power of any other system. ABS only activates when a vehicle's wheels are about to lock.

3. An Anti-Lock Braking System (ABS):

Is not available for vehicles with air brakes.

Is not helpful in most driving situations.

Can help you maintain control when braking.

Anti-Lock Braking Systems (ABS) are compatible with air brakes and help a driver maintain control of their vehicle by preventing wheel lockup.

4. If an air compressor is belt-driven, the belt should be routinely checked to ensure that it is:

Thin.

Properly tightened.

Cracked.

If your vehicle has air brakes, the air compressor drive belt should be checked before each drive. Check the tightness of the belt and verify that it is in good condition.

5. A ____ allows a driver to gradually apply spring brakes.

Modulating control valve

Trailer air supply control

Relay valve

A modulating control valve allows a driver to gradually apply spring brakes. In equipped vehicles, the valve is controlled by a lever located on the dashboard.

6. When an S-cam turns inside a brake drum, the S-cam:

Presses the brake shoes against the inside of the brake drum.

Presses the brake shoes against the brake linings.

Presses the brake linings against the wheel axles.

When a brake pedal is pressed and the S-cam is turned, the S-cam presses the brake shoes against the inside of the brake drum. This causes friction and will cause the vehicle to slow.

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