Podcast
Questions and Answers
Excessive use of the service brakes results in overheating, which can lead to:
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?
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:
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.
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.
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?
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?
The driver must be able to see a warning before air pressure in the service tanks falls below ___ psi.
The driver must be able to see a warning before air pressure in the service tanks falls below ___ psi.
The parking or emergency brake on a heavy vehicle can only be held in position by something that cannot leak away, like:
The parking or emergency brake on a heavy vehicle can only be held in position by something that cannot leak away, like:
Before driving a truck or bus with a dual air brake system, the pressure in each system should be at least ___ psi.
Before driving a truck or bus with a dual air brake system, the pressure in each system should be at least ___ psi.
The brake system that applies and releases the brakes when the driver uses the brake pedal is the ___ brake system.
The brake system that applies and releases the brakes when the driver uses the brake pedal is the ___ brake system.
Controlled braking:
Controlled braking:
Under normal conditions, to engage the parking brakes the driver must first:
Under normal conditions, to engage the parking brakes the driver must first:
Total stopping distance for vehicles with air brakes is longer than that for vehicles with hydraulic brakes due to ___ distance.
Total stopping distance for vehicles with air brakes is longer than that for vehicles with hydraulic brakes due to ___ distance.
Some air brake systems have an alcohol evaporator. What may happen if you don't keep the unit filled with alcohol?
Some air brake systems have an alcohol evaporator. What may happen if you don't keep the unit filled with alcohol?
Which of these is not a proper time to apply the parking brakes?
Which of these is not a proper time to apply the parking brakes?
A truck with air brakes going 55 MPH would require a stopping distance of:
A truck with air brakes going 55 MPH would require a stopping distance of:
If your vehicle has an alcohol evaporator, it is there to:
If your vehicle has an alcohol evaporator, it is there to:
The important thing to do when a low air pressure warning comes on is:
The important thing to do when a low air pressure warning comes on is:
The application pressure gauge shows how much air pressure you:
The application pressure gauge shows how much air pressure you:
What is emergency stab braking?
What is emergency stab braking?
When you apply the brakes, the brake shoes/linings are pressed against the:
When you apply the brakes, the brake shoes/linings are pressed against the:
The use of air brakes on a downgrade is only a supplement to the:
The use of air brakes on a downgrade is only a supplement to the:
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:
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:
All air brake equipped vehicles have:
All air brake equipped vehicles have:
If you must make an emergency stop, brake so you:
If you must make an emergency stop, brake so you:
The safety valve is usually set to reduce air pressure at ___ psi.
The safety valve is usually set to reduce air pressure at ___ psi.
During normal driving, spring brakes are usually held back by:
During normal driving, spring brakes are usually held back by:
In air brake vehicles, the parking brakes should be used:
In air brake vehicles, the parking brakes should be used:
The braking power of the spring brakes:
The braking power of the spring brakes:
The brake pedal in an air brake system:
The brake pedal in an air brake system:
The air loss rate for a straight truck or bus with the engine OFF and the brakes on should not be more than:
The air loss rate for a straight truck or bus with the engine OFF and the brakes on should not be more than:
Repeatedly pressing and releasing (fanning) the brake pedal may result in:
Repeatedly pressing and releasing (fanning) the brake pedal may result in:
For air brake systems in good condition, the air compressor should start pumping at about ___ psi.
For air brake systems in good condition, the air compressor should start pumping at about ___ psi.
The air compressor governor controls:
The air compressor governor controls:
The driver must be able to see a low air pressure warning which comes on before pressure in the service tank falls below ____ psi.
The driver must be able to see a low air pressure warning which comes on before pressure in the service tank falls below ____ psi.
The most common type of foundation brake found on heavy vehicles is the:
The most common type of foundation brake found on heavy vehicles is the:
The air brake lag distance at 55 MPH on dry pavement adds about ___ feet to your stopping distance.
The air brake lag distance at 55 MPH on dry pavement adds about ___ feet to your stopping distance.
If your truck or bus has dual parking control valves, you can use pressure from a separate tank to:
If your truck or bus has dual parking control valves, you can use pressure from a separate tank to:
The stop light switch:
The stop light switch:
If the spring brakes are on, when should you push the brake pedal?
If the spring brakes are on, when should you push the brake pedal?
What is emergency controlled braking?
What is emergency controlled braking?
Truck and bus parking or emergency brakes must be held on by:
Truck and bus parking or emergency brakes must be held on by:
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.
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.
If your truck has a dual air system and one of the systems is low on pressure:
If your truck has a dual air system and one of the systems is low on pressure:
If your truck's air compressor has its own oil supply, when should you first check the oil level?
If your truck's air compressor has its own oil supply, when should you first check the oil level?
You should know when your brakes are fading when:
You should know when your brakes are fading when:
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.
Studying That Suits You
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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.
