DMV Class B License Test: Air Brakes Flashcards

Questions and Answers

Excessive use of the service brakes results in overheating, which can lead to:

Expansion of the brake drums (correct)

Increased contact between the brake drums and brake linings

Improper adjustment of the S-cam

If air pressure does NOT build up to normal within the correct amount of time, what should you expect?

The alcohol container may be low

You should be ready to use your parking brake to help stop

Your air pressure may drop too low during driving (correct)

If you must make an emergency stop, you should brake so you:

Use the hand brake before the brake pedal

Use the full power of the brakes to lock them

Can steer and your vehicle stays in a straight line (correct)

The proper method of braking when going down long and/or steep grades, after selecting the proper gear, is to brake until your speed is about ___ MPH below your 'safe' speed, then release your brakes.

5 Signup and view all the answers

Your bus or truck has a dual air brake system. If a low air pressure warning comes on only for one system, what should you do?

Stop and safely park. Continue only after the system is fixed Signup and view all the answers

The driver must be able to see a warning before air pressure in the service tanks falls below ___ psi.

60 Signup and view all the answers

The parking or emergency brake on a heavy vehicle can only be held in position by something that cannot leak away, like:

Spring pressure Signup and view all the answers

Before driving a truck or bus with a dual air brake system, the pressure in each system should be at least ___ psi.

100 Signup and view all the answers

The brake system that applies and releases the brakes when the driver uses the brake pedal is the ___ brake system.

Service Signup and view all the answers

Controlled braking:

Is used to keep a vehicle in a straight line when braking Signup and view all the answers

Under normal conditions, to engage the parking brakes the driver must first:

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

Total stopping distance for vehicles with air brakes is longer than that for vehicles with hydraulic brakes due to ___ distance.

Brake lag Signup and view all the answers

Some air brake systems have an alcohol evaporator. What may happen if you don't keep the unit filled with alcohol?

Ice may form in the air storage tanks and cause the brakes to fail Signup and view all the answers

Which of these is not a proper time to apply the parking brakes?

When you come down a steep grade and your brakes are very hot Signup and view all the answers

A truck with air brakes going 55 MPH would require a stopping distance of:

More than 300 feet Signup and view all the answers

If your vehicle has an alcohol evaporator, it is there to:

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

The important thing to do when a low air pressure warning comes on is:

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

The application pressure gauge shows how much air pressure you:

Are applying to the brakes Signup and view all the answers

What is emergency stab braking?

Brake hard, release the brakes when the wheels lock, and reapply the brakes when the wheels start rolling Signup and view all the answers

When you apply the brakes, the brake shoes/linings are pressed against the:

Brake drum or disc Signup and view all the answers

The use of air brakes on a downgrade is only a supplement to the:

Braking effect of the engine Signup and view all the answers

Your truck has a properly functioning dual air brake system and minimum size air tanks. The air pressure should build from 85 to 100 psi within:

45 seconds Signup and view all the answers

All air brake equipped vehicles have:

An air supply pressure gauge Signup and view all the answers

If you must make an emergency stop, brake so you:

Can steer your vehicle in a straight line Signup and view all the answers

The safety valve is usually set to reduce air pressure at ___ psi.

150 Signup and view all the answers

During normal driving, spring brakes are usually held back by:

Air pressure Signup and view all the answers

In air brake vehicles, the parking brakes should be used:

Any time the vehicle is parked Signup and view all the answers

The braking power of the spring brakes:

Depends on the service brakes in adjustment Signup and view all the answers

The brake pedal in an air brake system:

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

The air loss rate for a straight truck or bus with the engine OFF and the brakes on should not be more than:

3 psi in one minute Signup and view all the answers

Repeatedly pressing and releasing (fanning) the brake pedal may result in:

The loss of brake air pressure Signup and view all the answers

For air brake systems in good condition, the air compressor should start pumping at about ___ psi.

100 Signup and view all the answers

The air compressor governor controls:

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

The driver must be able to see a low air pressure warning which comes on before pressure in the service tank falls below ____ psi.

60 Signup and view all the answers

The most common type of foundation brake found on heavy vehicles is the:

S-cam drum Signup and view all the answers

The air brake lag distance at 55 MPH on dry pavement adds about ___ feet to your stopping distance.

32 Signup and view all the answers

If your truck or bus has dual parking control valves, you can use pressure from a separate tank to:

Release spring emergency/parking brakes to move a short distance Signup and view all the answers

The stop light switch:

Turns on the brake lights to warn drivers behind you Signup and view all the answers

If the spring brakes are on, when should you push the brake pedal?

Never Signup and view all the answers

What is emergency controlled braking?

You apply the brakes as hard as you can without locking the wheels Signup and view all the answers

Truck and bus parking or emergency brakes must be held on by:

Mechanical force Signup and view all the answers

You are on a steep downgrade and have reached your 'safe' speed of 40 MPH. You would apply the service brakes until your speed drops to ___ MPH.

35 Signup and view all the answers

If your truck has a dual air system and one of the systems is low on pressure:

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

If your truck's air compressor has its own oil supply, when should you first check the oil level?

Before driving Signup and view all the answers

You should know when your brakes are fading when:

You have to push the brake pedal harder to control speed on a downgrade Signup and view all the answers

Study Notes

Air Brakes Fundamentals

Excessive service brake usage can cause brake drums to expand due to overheating.
Insufficient air pressure buildup can lead to low air pressure during driving, compromising safety.
In emergencies, brake application should allow for steering control and vehicle straightness.

Braking Techniques

When descending long grades, brake to 5 MPH below safe speed before releasing brakes.
If low air pressure warning activates in one of the dual air brake systems, stop and park safely until repairs are made.
Controlled braking helps maintain vehicle stability and alignment while braking hard.

Air Brake System Standards

A driver must see a low air pressure warning before pressure drops below 60 psi.
Parking brakes on heavy vehicles must rely on spring pressure, which does not leak away.
Minimum air pressure before driving a dual air brake vehicle should be at least 100 psi.

Brake System Operations

The service brake system controls brake application when using the brake pedal.
Emergency stab braking involves hard braking, releasing when wheels lock, then reapplying to regain control.
The brake shoes must contact either a brake drum or disc for effective braking.

Safety Protocols and Maintenance

The air compressor in healthy systems starts pumping at approximately 100 psi.
Ensure that all air brake vehicles are equipped with an air supply pressure gauge.
During normal operations, air loss rates should not exceed 3 psi in one minute with brakes applied and engine off.

Emergency Situations

When low air pressure warnings appear, the driver must safely stop and park as soon as possible.
The use of air brakes on downgrades should supplement the engine's braking effect and not serve as the primary braking mechanism.
Spring brakes must remain released while driving; never press the brake pedal with spring brakes applied.

Handling Steep Grades

To control speed on a steep downgrade, service brakes should reduce speed to 35 MPH if safe speed is 40 MPH.
The air brake lag distance adds roughly 32 feet to stopping distance at 55 MPH on dry surfaces.

Brake System Components

The safety valve typically activates at 150 psi to prevent excessive air pressure.
The air compressor governor regulates when air is pumped into the system, impacting overall brake functionality.

Brake Performance Tips

Brakes are fading when increased pressure is needed to maintain control on downgrades, signaling potential failure.
Parking brakes should always be engaged when the vehicle is parked to prevent movement when stationary.
Having an alcohol evaporator helps prevent ice formation in braking valves during cold conditions.

Good Practices in Air Brake Operations

Fanning the brake pedal can result in loss of brake air pressure; maintain steady pressure when needed.
Always check the oil level of air compressor systems before operating to ensure they function efficiently.
Understand emergency controlled braking as applying maximum pressure without locking wheels for better stability.

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Description

Prepare for the DMV Class B License test with these flashcards focusing on air brakes. Each card presents crucial information and questions to help ensure you understand the operation and maintenance of air brake systems. Perfect for candidates aiming to secure their air brakes endorsement.