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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 Texas CDL knowledge test. The TX 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 Texas CDL Manual. Take this TX CDL practice test now to prepare for the actual air brakes test!
1. When you make a quick lane change, the crack-the-whip effect can turn the trailer over. The crack-the-whip effect is caused by:
rearward amplification.
the rear trailer of a triple.
strong wind.
worn tire tread.
2. Which of the following is not a way to know when to change gears?
Check that the pressure gauge shows normal oil pressure
Use road speed (mph)
Watch your tachometer
Use engine speed (rpm)
3. Air tanks usually hold enough compressed air to allow the brakes to be used _________ even if the compressor stops working.
for 3 days
for one stop
several times
for one day
4. The spring brakes come on:
when main air pressure is lost.
when you bring the vehicle to a complete stop right away.
when air pressure in both air brake systems rises to a value set by the manufacturer.
when you lose ABS control.
5. Your mirrors should be adjusted so that:
a part of the vehicle is visible in the mirror.
more than half of the mirror shows the vehicle.
the rear of the vehicle is visible in the mirror.
no part of the vehicle is visible in the mirror.
6. What factors can cause brakes to fade or fail?
Overheating, low air pressure or water in the air tanks.
Not pressing the brake pedal hard enough.
Going too slow.
Not taking your foot off the accelerator.
7. Supply pressure gauges tell drivers:
how much air pressure they are applying to the brakes.
how much pressure is in the air tanks.
how much pressure the relay valves should send to the trailer brakes.
All of the above.
8. Foundation brakes are used:
only with the right wheels.
only with the front wheels.
only with the rear wheels.
at each wheel.
9. When driving on long and/or steep downgrades, to select an appropriate safe speed you should consider:
the length of the grade.
the road conditions.
the total weight of the vehicle and cargo.
All of the above.
10. Which of the following is NOT part of the air brake system?
Service brake system
Anti-lock brake system
Parking brake system
Emergency brake system
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TX CDL Air Brakes Test

Number of questions: 25
Correct answers to pass:20
Passing score:80%
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