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CDL Permit > Air Brakes > Flashcards

Air Brakes Flashcards

1
Q

The application pressure gauge shows how much air pressure you:

A

Are applying to the brakes

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2
Q

The spring brakes used on the chambers in a straight truck will bring you to a stop when air pressure drops below ___ psi (pound per square inch).

A

20

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3
Q

Some air brakes have an alcohol evaporator. What may happen if you don’t keep the proper level of alcohol?

A

Ice may form in the air brake valves and cause brake failure

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4
Q

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

A

Bring vehicle to a complete stop immediately and safely park. Continue only after issue is fixed.

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5
Q

Why drain water from compressed air tanks?

A

Water can freeze in cold weather and cause brake failure.

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6
Q

The safety valve is set automatically when pressure is:

A

150

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7
Q

Your truck has a dual air system and one of the system loses its pressure. What will happen?

A

Either the front or back brake will not be fully operational.

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8
Q

Parking or emergency brakes of the trucks and buses can be legally held on by ____ pressure.

A

Spring

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9
Q

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

A

Release the spring emergency/parking brakes to move a short distance

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10
Q

If your truck has a properly functioning dual air brake system and minimum size air tanks, the air pressure should build up from 85 to 100 psi within how many seconds?

A

45

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11
Q

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

A

Park on level ground, wait until normal air pressure is reached, release the parking brake and move forward slowly at about 5 mph. Then apply the brakes firmly.

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12
Q

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

A

2

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13
Q

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

A

Air pressure

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14
Q

The air compressor stops pumping air at what psi?

A

125

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15
Q

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

A

60

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16
Q

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

A

Expansion of the brake drums

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17
Q

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

A

S-cam drum

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18
Q

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

A

Can keep your vehicle in a straight line

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19
Q

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?

A

Stop right away and safely park. Continue only after the system is fixed

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20
Q

If your vehicle has an alcohol evaporator, every day during cold weather you should:

A

Check and fill the alcohol level

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21
Q

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

A

3 psi in one minute

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22
Q

The braking power of the spring brakes:

A

Depends on the service brakes being in adjustment

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23
Q

The air brake lag distance at 55 mph on dry pavement adds about ___ feet.

A

32

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24
Q

Total stopping distance for air brakes is longer than that for hydraulic brakes due to ____ distance.

A

Brake lag

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25
Q

It is accepted that too much heat caused by using your brakes too often can also cause:

A

Brake to fade or fail

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26
Q

Repeatedly partially increasing and pressing the brake pedal may result in:

A

A loss of brake air pressure

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27
Q

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

A

Service

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28
Q

A slack adjuster’s free play needs to be adjusted if it is more than about _____ when you pull hard on It.

A

1 inch

29
Q

An air brake system is fully charged at what psi?

A

125

30
Q

The brake pedal in an air brake system:

A

Controls the air pressure applied to the brakes

31
Q

The S-cam:

A

Forces the brake shoes against the inside of the brake drum

32
Q

Under normal conditions, in order to engage the parking brakes the driver should:

A

Apply brakes by pulling the parking brake control knob out

33
Q

All air brake equipped vehicles have:

A

A supply pressure gauge

34
Q

With air brake vehicles, the parking brake should be used:

A

Whenever you leave the vehicle unattended

35
Q

If the air compressor should develop a leak, what keeps the air in the tanks?

A

The one-way check valve

36
Q

Which of these is NOT a proper time to apply the parking brakes?
• If you will be stopping for only one hour.
• If you are going to test the parking brake to make sure that it holds the vehicle.
• If the brakes are very hot (e.g. Just after coming down a steep grade.

A

If the brakes are very hot (e.g. Just after coming down a steep grade.

37
Q

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

A

Any time when vehicle is parked

38
Q

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

A

Never

39
Q

To check the free play of manual slack adjusters of S-cam brakes, you should park on:

A

Level ground, chock the wheels and release the parking brakes.

40
Q

Excessive heat caused by using your brakes too often can also cause:

A

Brake to fade or fail

41
Q

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

A

Can steer and keep your vehicle in a straight line

42
Q

The use of brakes on a long and steep downgrade under normal conditions is only a supplement to:

A

The braking effect of the engine

43
Q

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

A

Stop and safely park as soon as possible

44
Q

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

A

Spring pressure

45
Q

Air braking takes more time than hydraulic braking because:

A

Air brakes take more time to flow through the lines than hydraulic fluid.

46
Q

When brakes are applied, the brake shoes will press against the:

A

Brake drum or disc

47
Q

The safety valve discharges automatically at the pressure of:

A

150 psi

48
Q

What is the correct way to stab brake?

A

Apply your brakes all the way. Release the brakes when wheels lock up. As soon as the wheels start rolling, apply the brakes fully again.

49
Q

If air pressure is not built up within the correct amount of time, then:

A

Air pressure may drop to a low point while driving, requiring an emergency stop

50
Q

The safety valve reduces pressure at ___ psi.

A

150

51
Q

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

A

Spring pressure

52
Q

The supply pressure gauge shows how much pressure:

A

Is in the air tanks

53
Q

The braking power of the spring brakes:

A

Depends on the brakes being in adjustment

54
Q

It is not safe to drive a vehicle that has brake drums with cracks that are longer than ___ of the width of the friction area.

A

1/2

55
Q

Your brakes are fading when:

A

You have to push harder on a brake pedal to control your speed on a downgrade

56
Q

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

A

Reduce the risk of icing in air brake valves in cold weather

57
Q

The air compressor governor controls:

A

When air is pumped into the air tanks.

58
Q

Modern air brakes combine three different systems. They are the service, the parking, and the _________
brakes.

A

Emergency

59
Q

If you do not have automatic tank drains, how often should you drain the oil and water from the bottom of compressed air storage tanks?

A

At the end of each day of driving

60
Q

The proper use of the brakes when going down a long steep grade after selecting a proper gear is to brake until your speed is about ___ below the posted speed and release your brake.

A

5 mph

61
Q

In ideal conditions a truck or bus with air brakes going at 55 mph would require the stopping distance of how many feet?

A

More than 300 feet

62
Q

When is it OK to leave your truck unattended without applying the parking brakes and choking the wheels?

A

Never

63
Q

The stop light switch:

A

Turns on the brake lights when you put on the air brakes

64
Q

The _____________ shows how much pressure is in the air tanks m.

A

Supply pressure gauge

65
Q

To test air service brakes you should:

A

Brake firmly while slowly moving forward

66
Q

If you are driving down a steep downgrade and have reached your safe speed of 40 mph, you would apply the service brake until your speed dropped to ___ mph.

A

35

67
Q

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

A

Either the front or rear brakes will not be fully functional

68
Q

What happens when your brake drums get very hot?

A

They expand

69
Q

What is a “Wig Wag”?

A

A mechanical arm that signals low air pressure.

CDL Permit (3 decks)

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