Air Brake System Quiz & Flashcards: Brake Lag Distance

Questions and Answers

You should know that your brakes are fading when?

You have to push harder on the brake pedal to control your downhill speed.

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

Never

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

A loss of air pressure.

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

60 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 the Emergency/Spring/Parking brakes to move a short distance. Signup and view all the answers

The brake pedal in the air brake system?

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

To check the free play of manual slack adjusters of S-Cam brakes, you should?

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

Parking or emergency brakes on trucks or buses can be legally held on by ___________ pressure.

Spring Signup and view all the answers

Emergency stab braking is when you?

Brake as hard as you can, then release the brakes when the wheels lock up, and put on the brakes again when the wheels start rolling. Signup and view all the answers

The most common type of foundation brakes found on heavy vehicles is the?

S-Cam. Signup and view all the answers

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

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

The most important thing to do when a low pressure warning light comes on is to?

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

With air brake equipped vehicles, the parking brakes should be used?

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

The air compressor governor controls?

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

The stop light switch?

Turns on the brake light to warn other drivers behind you. 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 loss rate for a straight truck or bus with the engine off and the parking brakes off and the service brakes on should not be more than?

3 PSI in one minute. Signup and view all the answers

The braking power of the spring brakes?

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

How should you check spring brakes application when air pressure drops below a certain level?

Park on level ground, chock wheels, release parking brake when you have enough pressure, shut the engine off and repeatedly press and release the pedal. Signup and view all the answers

If you are driving down a steep grade and have reached a safe speed of 40 MPH you would apply the service brakes until your speed drops to _____ MPH.

35 Signup and view all the answers

Air brake lag distance at 55 MPH adds about _____ feet to your stopping distance.

32 Signup and view all the answers

How should you check that your service brakes are working properly?

Park on level ground, wait for normal air pressure, release the parking brake, move forward slowly and apply the brakes firmly using the brake pedal. Signup and view all the answers

Emergency controlled braking is when you?

Apply the brakes as hard as you can without locking up the brakes. Signup and view all the answers

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

If the brakes are very hot (just after coming down a steep grade) Signup and view all the answers

All air brake equipped vehicles have?

A supply air pressure gauge. Signup and view all the answers

If air pressure does not build up to normal within the correct amount of time then?

Your air pressure may drop too low during driving requiring an emergency stop. Signup and view all the answers

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

Expansion of the brake drums. Signup and view all the answers

The proper method of braking when going down a long and/or steep grade, 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

Under normal conditions in order 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 air brakes is longer than for hydraulic brakes due to?

Brake Lag. Signup and view all the answers

If you must make an emergency stop you should brake so you?

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

The parking or emergency brakes 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

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

Ice may form in the air storage tanks or air lines and cause brakes to fail. 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

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

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

Stop right away and safely park the truck, continue only after the system is fixed. Signup and view all the answers

What happens when your brake drums get very hot?

They expand. Signup and view all the answers

How often should the air tanks be drained?

Daily. Signup and view all the answers

An air application gauge shows?

How much air pressure you are applying to the brakes. Signup and view all the answers

The difference between controlled braking and stab braking is?

Controlled braking does not lock the wheels, stab braking involves locking the wheels. Signup and view all the answers

Front brake limiting valves reduce the air pressure applied to the front brakes by?

1/2. Signup and view all the answers

To charge/release the brakes with air you must?

Push the valves in. Signup and view all the answers

The tractor air supply valve is what color?

Yellow. Signup and view all the answers

When the engine is at operating RPM the pressure should build up to 85 to 100 PSI within ______ seconds in dual air systems.

45 seconds. Signup and view all the answers

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

1/2. Signup and view all the answers

In single air systems (pre 1975) air pressure should build from 50-90 PSI within _____ minutes.

<ol start="3"> <li></li> </ol> Signup and view all the answers

In air operated disc brakes air pressure acts on a brake chamber and slack adjuster like S-Cam brakes but instead of the S-Cam a _______ is used.

Power Screw. Signup and view all the answers

A safety relief valve is used to protect the air system from too much air pressure. This valve is usually set to open at ______PSI.

<ol start="150"> <li></li> </ol> Signup and view all the answers

Tractor and straight truck spring brakes will apply fully when air pressure drops to a range of _____ PSI.

20-45. Signup and view all the answers

On large buses it is common for the low pressure warning device to signal at _____ PSI.

80-85. Signup and view all the answers

Study Notes

Air Brakes Overview

Brake fading occurs when more force is needed on the brake pedal to manage downhill speeds.
Spring brakes should never be engaged while pressing the brake pedal.
Fanning the brake pedal can lead to a loss of air pressure.

Air Pressure Monitoring

A low air pressure warning activates before falling below 60 PSI.
Brake systems may be compromised if one part of a dual air brake system is low on pressure.

Brake Functionality

The brake pedal regulates air pressure for braking.
Parking or emergency brakes in heavy vehicles rely on spring pressure.
Service brakes must be adjusted for spring brakes to function effectively.

Brake Testing and Maintenance

Check slack adjusters by parking on level ground and manipulating the adjusters.
Air tanks must be drained daily to prevent water buildup and ensure functionality.
Inspect brake drums for any cracks exceeding half the friction area width.

Emergency Procedures and Braking Techniques

Emergency stab braking involves applying full brake pressure, releasing when wheels lock, and re-applying when they begin rolling.
Controlled braking allows for steering without wheel lock-up.
The safest speed to resume brakes after descending a steep grade is 35 MPH.

Brake Characteristics

Air brake systems generally have a longer stopping distance than hydraulic brakes due to brake lag.
The air compressor typically starts pumping air into the tanks at around 100 PSI.
Total stopping distance includes air brake lag which adds roughly 32 feet at 55 MPH.

Operational Protocols

Use parking brakes whenever the vehicle is parked.
If air pressure does not build to normal quickly, it can necessitate an emergency stop.
A supply air pressure gauge is standard on all air brake-equipped vehicles.

Warnings and Indicators

The stop light switch alerts surrounding drivers when brakes are applied.
Low pressure warnings prompt immediate safe parking.
Low pressure warnings in dual systems require immediate attention.

Additional Components

Power screws replace S-Cams in air-operated disc brakes.
Excessive use of service brakes can cause overheating and drum expansion.
The tractor air supply valve is identifiable by its yellow color.

General Best Practices

Maintain proper brake function by checking service brakes through controlled movements.
Ensure that alcohol evaporators are filled to avoid ice formation in air lines.
Front brake limiting valves decrease pressure by half to maintain control.

Contextual Facts

The air loss rate for straight trucks should not exceed 3 PSI in one minute when the engine is off and brakes are applied.
The pressure in dual air brake systems should equal at least 100 PSI before operation.
Emergency brake systems are designed to retain pressure without leaks, utilizing spring pressure for safety.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Test your knowledge of air brakes with these flashcards. The quiz covers essential concepts related to braking systems, including proper usage and warning signs of brake failure. Ideal for truck drivers and transportation professionals preparing for their tests.

Air Brakes Test Flashcards