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 four answer choices. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the Colorado 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. Where is the safety relief valve usually located?

Near the rear brake

Near the front brake

In an air tank

On the dashboard

An air brake system's safety relief valve is located in the tank that is first to receive air from the compressor.

2. Friction inside a brake drum is caused when the brake shoes and linings:

Push against each other.

Separate from the axle.

Push against the inside of the drum.

Create excess heat.

Friction inside a brake drum is caused when the brake shoes and linings push against the inside of the drum. The friction in the drums will slow and stop the vehicle.

3. In a dual air brake system:

Each system has separate air tanks, hoses, and lines.

The systems share air tanks, but each has its own separate hoses and lines.

Each system uses the same lines and hoses.

One system is the main braking system and a second system is ready to be used if the first one fails.

A dual air brake system is made up of two separate air brake systems. The systems share a single set of brake controls, but each has its own air tanks, hoses, and lines.

4. What can happen if the air pressure gets too low in an air brake system?

The brakes may squeak.

The brakes may not work.

The brakes may be sluggish.

The brakes will be very sensitive.

Pressing and releasing the brake pedal unnecessarily can let air out faster than the compressor can replace it, reducing the available air pressure. If the air pressure in an air brake system gets too low, the brakes will no longer work.

5. Most heavy-duty vehicles use:

Single air brake systems.

Dual air brake systems.

Triple air brake systems.

Quadruple air brake systems.

Most heavy-duty vehicles use dual air brake systems, in which there are two separate braking systems operated by a single set of controls. Each system operates the brakes on different axles.

6. How many air storage tanks are used in an air brake system?

Two tanks

Four tanks

Six tanks

The number varies.

Air storage tanks are used to hold compressed air. The number and size of air tanks in an air brake system varies among vehicles.

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