Alabama CDL General Knowledge

Questions and Answers

When should you drain the air tanks?

After every working day

What is the S-cam used for?

To put on the brakes

What makes the total stopping distance for air brakes longer than hydraulic brakes?

Brake lag distance

What is the brake system that applies and releases the brakes when the driver uses the brake pedal?

Service brake system Signup and view all the answers

What should you do to make an emergency stop using the stab braking method?

Brake as hard as you can, get off of the brakes when the wheels lock, and get back on the brakes when the wheels start rolling again Signup and view all the answers

Brake lag distance at 55 mph is ______ feet.

32 Signup and view all the answers

If your vehicle has an alcohol evaporator, what is its purpose?

Reduce the risk of ice in air brake valves in cold weather Signup and view all the answers

What can legally hold a parking or emergency brake in position for a truck, truck tractor, or bus?

Spring pressure Signup and view all the answers

The braking power of the spring brakes depends on what?

The adjustment of the service brake Signup and view all the answers

What should you do before leaving the vehicle unattended?

Set the parking brake, remove the keys, and chock the wheels Signup and view all the answers

Under what conditions are front-wheel brakes good?

All weather conditions Signup and view all the answers

What happens if the air tanks are not drained?

Your brakes may fail because of water freezing Signup and view all the answers

What does an anti-lock braking system (ABS) do?

Activates when your wheels are about to lock up Signup and view all the answers

What can cause brakes to fade or fail?

Excessive use of the service brake, not relying enough on the engine braking, and brakes being out of adjustment Signup and view all the answers

If your vehicle has a properly functioning dual air brake system, the air pressure should build from 85 to 100 psi within ______ seconds.

45 Signup and view all the answers

The air compressor will stop pumping air to the air brakes at ______ psi.

125 Signup and view all the answers

What can excessive heat from overuse of the service brakes cause?

The brakes to fade Signup and view all the answers

What is the typical air brake system fully charged at?

125 psi Signup and view all the answers

During normal driving, spring brakes are normally held back by?

Air pressure Signup and view all the answers

What should you do during your final air brake check if the air pressure does not build up fast enough?

The air pressure may drop too low during driving Signup and view all the answers

To test the static air leakage rate, what should you do?

Turn off the engine, release the parking brake, and let the engine settle Signup and view all the answers

What do air brakes use?

Compressed air Signup and view all the answers

What happens when you press the brake pedal?

Compressed air enters the brake chamber Signup and view all the answers

What does the air compressor governor control?

When air is pumped into the air tanks Signup and view all the answers

What should you do when a low air pressure signal comes on?

Stop and park as soon as possible Signup and view all the answers

What must air brake-equipped vehicles have?

A supply pressure gauge Signup and view all the answers

What is the minimum leakage rate for brake drums?

1/2 Signup and view all the answers

If the low pressure warning signal is not working, what might happen?

It may lead to sudden emergency braking in a single circuit air system Signup and view all the answers

In the event of a brake system failure, what does the emergency brake system use to stop the vehicle?

Parts of the service brake and parking brake Signup and view all the answers

What should you never do if the spring brakes are on?

Press the brake pedal Signup and view all the answers

How do you know your brakes are fading?

You have to press the brake pedal harder than usual to control your speed Signup and view all the answers

What does a converter dolly with anti-lock brakes (ABS) need to have?

A yellow lamp on the left side Signup and view all the answers

Which of the following is the most important thing about hard braking?

Do not lock the wheels for longer than an instant Signup and view all the answers

In controlled braking, you should ?

Brake in a straight line Signup and view all the answers

What could happen to the brakes if oil and water collect in the air tanks?

The brakes could fail Signup and view all the answers

Why is it called an S-cam?

It is shaped like the letter 'S' Signup and view all the answers

What should you do to test the air service brakes?

Brake firmly while slowly moving forward Signup and view all the answers

When can you leave your truck unattended without first applying the parking brakes or chocking the wheels?

Never Signup and view all the answers

If your truck or bus has a dual parking control valve, what does it mean?

You can use pressure from a separate tank to release the spring brakes to move a short distance Signup and view all the answers

The brake pads should be ______ for the brakes to be on.

Against the drum Signup and view all the answers

The application pressure gauge shows how much air pressure?

Is being applied to the brakes Signup and view all the answers

What keeps the air in the tanks if the air compressor develops a leak?

The one-way check valve Signup and view all the answers

Brake drums must not have cracks longer than ______ the width of the fractioned area.

1/2 Signup and view all the answers

What is the maximum acceptable leakage rate per minute for single vehicles?

3 psi Signup and view all the answers

How do brakes work on a long, steep downgrade?

They work as a supplement to the braking effect of your engine Signup and view all the answers

How would you check your truck's slack adjusters?

Use gloves and pull on each slack adjuster that you can reach Signup and view all the answers

What does the parking brake control do?

Lets the air out of the brake chamber Signup and view all the answers

What could happen if the low pressure warning signal is not working?

It may lead to sudden emergency braking in a single circuit air system Signup and view all the answers

If your vehicle has dual air brake systems, what happens if one system loses air pressure?

Either the front or rear brakes will not be fully operational Signup and view all the answers

Under ideal conditions, what is the average stopping distance for a bus or truck equipped with air brakes traveling at 55 mph?

More than 400 feet Signup and view all the answers

What do modern air brake systems combine?

The service, parking, and emergency brakes Signup and view all the answers

What should you do to check the free play of manual slack adjusters on S-cam brakes?

Park on level ground, chock the wheels, and release the parking brakes Signup and view all the answers

If a low air pressure warning comes on for only one system in a dual air brake system, what should you do?

Stop. Safely park and only continue after the vehicle has been fixed Signup and view all the answers

If your vehicle has an alcohol evaporator, what should you do during cold weather every day?

Check and fill the alcohol level Signup and view all the answers

With S-cam drum brakes, when the brake chamber fills with air, air pressure pushes the push rod out, moving the and thus rotating the .

Slack adjuster; brake camshaft Signup and view all the answers

In which position should you NOT apply the parking brake?

If the brakes are very hot Signup and view all the answers

What can cause brakes to fail or fade?

Overheating, low air pressure, and not relying on the engine braking effect Signup and view all the answers

If you need to stop quickly and your vehicle lacks anti-lock brakes (ABS), what methods can you use?

Controlled braking method or stab braking method Signup and view all the answers

Tractor and straight truck spring brakes will come fully on when air pressure drops to a range of ______.

20 to 45 psi Signup and view all the answers

What does the modulating control valve allow you to control?

Spring brakes Signup and view all the answers

What should air loss in a straight truck or bus not exceed with the engine off and the brakes applied?

3 psi in one minute Signup and view all the answers

What activates the stop switch?

Air pressure Signup and view all the answers

A straight truck or bus air brake system should not leak at a rate of more than ______ psi per minute with the engine off and the brakes released.

2 Signup and view all the answers

What is required for vehicles with air brakes?

An air pressure gauge to show the pressure available for braking Signup and view all the answers

Slack adjusters should not have any more than ______ of play.

1/2 inch Signup and view all the answers

What is the best way to test your vehicle's low air pressure warning system?

With the engine off, step off and on the brakes and see if the signal light comes on Signup and view all the answers

Which vehicle must have low air pressure warning signals?

All of them Signup and view all the answers

On a long or steep downgrade, once you have reached your safe speed, brake until you are traveling ______ lower than the safe speed.

5 mph Signup and view all the answers

To apply the parking brake under normal conditions, you should?

Let the air out of the brake chambers Signup and view all the answers

What are slack adjusters?

Slack adjusters are an important part of your air brake system that allows you to adjust the brakes to ensure they are safe Signup and view all the answers

Why does air braking take more time than hydraulic braking?

Air brakes need to have air in the lines to work Signup and view all the answers

What does the brake pedal in an air brake system control?

The air pressure applied to put on the brakes Signup and view all the answers

What does the tractor protection valve do?

Keeps air in the tractor or truck brake system Signup and view all the answers

What is the first thing you should do if the low air pressure warning comes on?

Stop Signup and view all the answers

When should you use the parking brake?

Every time you leave the vehicle Signup and view all the answers

What does the supply pressure gauge show?

Is in the air tanks Signup and view all the answers

Which of the following is not a part of the drum brake?

Safety valve Signup and view all the answers

Study Notes

General Air Brake Knowledge

Oil and water can collect in compressed air tanks; drain them after every working day if no automatic tank drain is present.
The S-cam is a critical component used to apply the brakes.
Total stopping distance for air brakes is extended due to brake lag distance.

Brake Systems

The service brake system is responsible for applying and releasing brakes when the driver uses the brake pedal.
To make an emergency stop using air brakes, utilize the stab braking method correctly to avoid wheel lock.
Brake lag distance at 55 mph is approximately 32 feet.

Air Brake Maintenance and Function

Alcohol evaporators help prevent ice formation in air brake valves during cold weather.
Spring pressure is legally allowed to hold a parking or emergency brake in position for heavy vehicles.
Proper adjustment of the service brake affects the braking power of the spring brakes.

Safety and Operational Procedures

Always set the parking brake, remove the keys, and chock the wheels before leaving a vehicle unattended.
Front-wheel brakes perform well under all weather conditions and should be checked consistently.
Failing to drain air tanks can lead to brake failure due to freezing water.

Anti-lock Systems and Braking Techniques

An anti-lock braking system (ABS) engages to prevent wheel lock-up.
Common causes of brake failure or fade include excessive service brake use, inadequate engine braking reliance, and improperly adjusted brakes.
If an ABS fails, normal brake function remains, but repairs should be made promptly.

Vehicle Specifications and Conditions

Dual air brake systems should build air pressure from 85 to 100 psi in about 45 seconds.
The air compressor governor stops pumping air at 125 psi.
The air pressure in a typical air brake system should be fully charged at 125 psi.

Braking Mechanics and Emergency Procedures

Maintain control and steer to stay in a straight line during emergency stops.
Vehicles must have a supply pressure gauge to monitor air pressure.
In case of low air pressure signals, safely stop and park as soon as possible.

Operational Limits and Regulations

Brakes should not lock up for prolonged periods during hard braking.
Always check for a proper function of the low air pressure warning signal to avoid sudden emergency braking situations.
Slack adjusters should be maintained at no more than 1/2 inch of play and checked regularly for safety.

Testing and Performance Standards

To test static air leakage, turn off the engine, release the parking brake, and allow the air system to settle.
Acceptable leakage rates for single vehicles is 3 psi per minute, while combination vehicles allow for 4 psi.
On steep downgrades, brake until your speed is 5 mph below the determined safe speed.

Additional Considerations

Be aware of the risks of overheating and the importance of engine braking to ensure effective brake operation.
The application pressure gauge displays the amount of air pressure applied to the brakes.
Routine checks on brake components, including slack adjusters and brake drums, ensure vehicle safety.

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Description

Test your knowledge of Alabama CDL general concepts with these flashcards. This quiz covers essential topics such as air brake maintenance, braking systems, and safety practices. Perfect for those preparing for their Commercial Driver's License in Alabama.