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The air brakes endorsement applies to applicants who wish to drive a vehicle with air brakes in Class A, B, or C CDL. To drive a vehicle with air brakes, you must pass the air brake component of the Missouri CDL knowledge test. The MO CDL air brakes test consists of 25 questions, and you'll need at least 20 correct answers to pass (80%). The test covers the information found in the air brakes section of the Missouri CDL Manual. Take this MO CDL practice test now to prepare for the actual air brakes test!
1.
Some vehicles have a separate air tank which can be used to:
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turn on the 4-way emergency flashers.
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release the spring brakes.
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hold the vehicle or combination of vehicles stationary.
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2.
If you must drive slowly, how should you alert following drivers?
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Flash your brake lights
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Turn on your taillights
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Use your emergency flashers if it is legal
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3.
Slack adjusters:
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regulate the distance between the rear wheels.
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regulate the distance that the air brake has to travel to apply friction to the wheel.
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should move more than one inch where the push rods attach to them.
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4.
Brake drums or discs must not have cracks longer than ____ the width of the friction area.
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1/2
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1/3
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1/4
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5.
The safety valve is usually set to open at:
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100 psi.
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150 psi.
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200 psi.
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6.
Which of the following is NOT TRUE? When you drive a tractor-trailer combination with ABS, you should:
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drive slower to keep your vehicle in a straight line.
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monitor your tractor and trailer as you slow down, and if it is safe to do so, back off the brakes to stay in control.
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brake the same way, regardless of whether you have ABS on the tractor, the trailer, or both.
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7.
If the air tanks are not drained:
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your speed must be reduced to 5 MPH below your “safe” speed.
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the air pressure in the tanks is reduced.
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the water can freeze in cold
weather and cause brake failure.
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8.
Some air brake systems have an alcohol evaporator to:
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reduce the stopping power of the vehicle.
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reduce the danger of slipping.
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prevent ice from forming in the brake system.
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9.
Truck tractors with air brakes built after March 1, 1997, are required to be equipped with:
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a rear backup camera.
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hydraulic brakes.
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anti-lock brakes.
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10.
Before driving a truck or bus with a dual air brake system, the minimum pressure in both the primary and secondary
systems should be at least:
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75 psi.
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130 psi.
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100 psi.
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