Air Brakes Free

How many seconds do you need to check the truck mirrors?

only if you need
Check mirrors every 25 to 30 seconds
Check mirrors every 8-10 seconds
If the traffic is heavy

If your truck or bus has dual parking control valves, you can use the air pressure from a separate air tank to do what?

Release the emergency spring brakes/hand brakes to move a short distance
Balance the service brake system when you are parking
You have to apply more pressure to the brakes if the main tank is low
All of the above

What does the front brake limiting valve in some older vehicles do when turned to “slippery”?

It reduces the air pressure in the front brakes to 3/4 that of normal conditions.
It cuts the air supply to the front brakes and increases the pressure in the rear brakes.
It decreases the air pressure to all brakes by half.
It cuts the standard air pressure to the front brakes by half.

What should you do if the low-air-pressure warning comes on?

Use stab braking until you stop.
Drive to the nearest rest area.
Stop your vehicle as quickly as possible and safely park it
Use a tire gauge to check the pressure of each tire

What should you do to stop a trailer jackknife?

Countersteer the steering wheel
Use the trailer hand brake
Release the service brakes
Use the disc brakes

Pressing and releasing the brake pedal quickly and repeatedly

Will stop your vehicle faster
Will help cool your brakes
Can let the air out faster than the compressor can replace it
All of the above

The low-air-pressure warning light must come on before the air pressure in the tanks falls below what psi level?

30
40
60
80

Air brake systems consist of three different braking systems which are then combined. What are these three braking systems?

The foundation brake system, the disc brake system, and the drum brake system
The disc brake system, the service brake system, and the manual brake system
The service brake system, the parking brake system, and the emergency brake system
The hard brake system , parking brake and trailer brake

Which of the following statements about using retarders are true?

It creates extra heat between the brake shoes or pads and drums or disks
Brakes used on a steep downgrade increases the engine brake effect
You should not use the retarder as the principal way of speed control
Can cause the drive wheels to skid

The brake brums or discs should not have cracks covering more than?

3/4 of friction area
1/2 of friction area
1/4 of friction area
4/4 of friction area

When braking on descents, what should you do?

Go slow enough so that a light and constant use of the brakes prevents you from accelerating.
Brake hard, then let the brakes cool.
Coast downhill, then apply the brakes hard.
Use puncture braking until the wheels lock, then release.

The brake pedal of the air brake system does what?

Control the air compressor speed
Control the air pressure when you apply the brakes
It is joint to the slack adjusters
Release the emergency spring brakes

Emergency controlled braking is when:

You apply the brakes as hard as you can without locking the wheels
Apply the brakes as hard as you can, release the brakes when you lock the wheels and apply the brakes again when the wheels start moving
Apply the hand valve for a second, then apply the brake pedal harder
Apply the brakes with half the force

A parking brake control in the cab allows the driver to?

Let air out of the spring brakes, and this lets the springs put the brakes on
Control the air of the tanks
Let air out of the brakes, but it doesn't let the springs put the brakes on
Lock the wheels with less effort

Wedge brakes have a chamber push rod. What does the push rod do?

The rod pushes a wedge directly between the ends of two brake shoes, shoving them apart and against the inside of the brake chamber.
The rod pushes a wedge directly between the ends of two brake shoes, shoving them apart and against the inside of the brake drum.
It pushes a wedge directly between the ends of the two brake pads, shoving them apart and against the inside of the brake chamber.
It pushes a wedge directly between the ends of two brake pads, shoving them apart and against the inside of the brake drum.

If you don’t have an automatic tank drain, how often should you drain the oil and water that collects at the bottom of the compressed air storage tank?

Once a week
After every 4 hours of service
At the end of each driving day
After every 6 hours of service

When is it acceptable to leave your truck unattended without applying the parking brakes or chocking the wheels?

Never
If you are doing a pre-trip inspection
If you will be far from the truck only for a few minutes
All of the above

Spring brakes do which of the following?

They use air pressure to stop the vehicle
They will not work if all the air leaks out of the air brake system
They are held by mechanical force
They will work normal

During normal driving, the spring brakes are held by?

Spring pressure
Air pressure
Bolts
Air disc

If your truck has a dual air system and one of the systems has low pressure, then?

Brake drums are not fully pressurized
The slack adjusters manuals of S-cam brakes are not on correctly
The front or the rear brakes will not be operating fully
All of the above

Some air brake systems have an alcohol evaporator. What is the purpose of the alcohol evaporator?

Helps evaporate alcohol, which can be harmful to the brake system
Helps reduce the risk of built-up sludge in the bottom of the air tank
Helps reduce the risk of ice in air brake valves and other parts
Helps break down harmful substances such as dirt, thus preventing them from entering the air tank

Pressing and releasing the brake pedal quickly and repeatedly can do what?

It will stop your vehicle faster.
It will help to cool the brakes.
It can let air out faster than the compressor can replace it.
Pumps air back into the air brake.

Why do you have to drain water from the compressed air tanks?

To prevent them from getting the oil dirty from oil compressor
The water can freeze in cold weather and cause brake failure
The lower level of boiling water reduce the brake power
Water can cause brake failure

A pressure gauge tells you how much air there is in:

Trailer brake lines
Tractor brake lines
Air tanks
Air governor

An air brake system is fully loaded when the tank is at what pressure?

125 psi
75 psi
100 psi
150 psi

When the brakes are applied, what are the brake shoes and linings are pushed against?

The brake pads
The inside of the drum
The brake lining
The inside of the brake chamber

Most newer heavy-duty vehicles use dual air brake systems for safety. A dual air brake system has:

Two separate air brake systems and two sets of brake controls
Two separate air brake systems and a single set of brake controls
One air brake system and two sets of brake controls
All of the above

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