Air Brakes Free CDL Practice Tests
Page 8

Prepare For The Air Brakes Portion Of Your CDL Written Exams

Air Brakes Questions

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On a long or steep downgrade, the foot brakes should be used:
  • As the only method of controlling speed
  • They should never be used
  • As much as possible
  • Sparingly and intermittently
Click here to look up the answer

From The CDL Manual

Proper Braking Technique —

Remember, the use of brakes on a long and/or steep downgrade is only a supplement to the braking effect of the engine. Once the vehicle is in the proper low gear, the following is the proper braking technique:

  • Apply the brakes just hard enough to feel a definite slowdown.
  • When your speed has been reduced to approximately 5 mph below your “safe” speed, release the brakes. (This brake application should last about 3 seconds.)
  • When your speed has increased to your “safe” speed, repeat steps 1 and 2.
Next
On a long or steep downgrade, how should vehicle speed be primarily controlled?
  • With the service brake
  • Free coasting
  • Swerving gently side-to-side
  • Through the braking effect of the engine
Click here to look up the answer

From The CDL Manual

Proper Braking Technique —

Remember, the use of brakes on a long and/or steep downgrade is only a supplement to the braking effect of the engine. Once the vehicle is in the proper low gear, the following is the proper braking technique:

  • Apply the brakes just hard enough to feel a definite slowdown.
  • When your speed has been reduced to approximately 5 mph below your “safe” speed, release the brakes. (This brake application should last about 3 seconds.)
  • When your speed has increased to your “safe” speed, repeat steps 1 and 2.
Prev
Next
If the low air pressure warning light comes on, you should:
  • Pump the brake pedal furiously
  • Immediately engage the emergency brake
  • Stop and park your vehicle as soon as it is safe to do so
  • Coast out-of-gear until the vehicle stops
Click here to look up the answer

From The CDL Manual

Low Air Pressure —

If the low air pressure warning light comes on, stop and safely park your vehicle as soon as possible. There might be an air leak in the system.

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Next
In case of a low air situation, the spring brakes should come on at:
  • Between 20 to 45 psi
  • 60 psi
  • 100 psi
  • 120 psi
Click here to look up the answer

From The CDL Manual

Controlled braking is possible only while enough air remains in the air tanks. The spring brakes will come on when the air pressure drops into the 20 to 45 psi range.

Prev
Next
The parking brake should be used:
  • When you need to stop quickly
  • Only when parked on an incline
  • Any time you park the vehicle
  • Only in an emergency
Click here to look up the answer

From The CDL Manual

Parking Brakes —

Any time you park, use the parking brakes, except as noted. Pull the parking brake control knob out to apply the parking brakes. Push it in to release them. The control will be a yellow, diamond-shaped knob labeled “parking brakes” on newer vehicles.

Prev
Next
The parking brake should not be used when wet in freezing temperatures, or:
  • If the brakes are very hot
  • First thing in the morning
  • In the desert
  • On flat ground
Click here to look up the answer

From The CDL Manual

Do not use the parking brakes if the brakes are very hot (i.e., from just coming down a steep grade), or if the brakes 69 are very wet in freezing temperatures. If the brakes are used when very hot, they can be damaged by the heat. If they are used in freezing temperatures when the brakes are very wet, they can freeze so the vehicle cannot move. Use wheel chocks to hold the vehicle. Let hot brakes cool before using the parking brakes. If the brakes are wet, use the brakes lightly while driving in a low gear to heat and dry them.

Prev
Next
If your brakes are wet, what should you do to dry them quicker?
  • Use a hair dryer
  • Park in the sun
  • Apply the brakes lightly while driving in a low gear
  • Speed up to 30 mph and apply the brakes very hard
Click here to look up the answer

From The CDL Manual

If the brakes are wet, use the brakes lightly while driving in a low gear to heat and dry them.

Prev
Next
Air tanks should be drained:
  • When the brakes start fading
  • At least at the end of every day
  • Whenever your dispatcher tells you to
  • Every 1000 miles
Click here to look up the answer

From The CDL Manual

If your vehicle does not have automatic air tank drains, drain your air tanks at the end of each working day to remove moisture and oil. Otherwise, the brakes could fail.

Prev
Next
The emergency spring brake release knob is:
  • Diamond and yellow
  • Round and yellow
  • Round and blue
  • Red and octogonal
Click here to look up the answer

From The CDL Manual

See Figure 5-4, Page 69 of the CDL manual

Prev
Next
The trailer air supply knob is usually:
  • Blue and round
  • Red and round
  • Yellow and diamond-shaped
  • Red and octogonal
Click here to look up the answer

From The CDL Manual

See Figure 5-4, Page 69 of the CDL manual

Prev
Next
The parking brake knob is usually:
  • Blue and round
  • Yellow and round
  • Yellow and diamond-shaped
  • Red and octogonal
Click here to look up the answer

From The CDL Manual

See Figure 5-4, Page 69 of the CDL manual

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