CDL AIR BRAKES PRACTICE TEST - NORTH CAROLINA
11.
In combination vehicles with air brakes, the trailer air supply control should pop out when the air pressure falls within the range of:
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50 to 75 psi
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100 to 120 psi
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20 to 45 psi
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10 to 20 psi
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12.
By pushing the trailer air supply control knob in, you:
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keeps air in the tractor or truck brake system.
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supply the trailer with air.
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supply the tires with air.
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shut the air off and put on the trailer emergency brakes.
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13.
The air brake lag distance at 55 mph on dry pavement adds about:
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75 feet.
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60 feet.
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32 feet.
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16 feet.
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14.
The low air pressure warning light is usually:
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yellow.
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blue.
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orange.
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red.
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15.
Tractor and straight truck spring brakes will come fully on when the air pressure drops to a range of:
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20 to 45 psi.
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55 to 74 psi.
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5 to 15 psi.
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30 to 35 psi.
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