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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 South Carolina CDL knowledge test. The SC 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 South Carolina CDL Manual. Take this SC CDL practice test now to prepare for the actual air brakes test!
1. Why should you check your mirrors regularly to know where other vehicles are around you?
To flash the brake lights if you are being tailgated.
To know whether you can make a quick lane change in an emergency.
To move out of their way if they want to get past.
To better assess your own speed.
2. Before starting down a hill, you should slow down and shift down:
to a gear that will cause your brakes to overheat.
to a speed that you can control without using the brakes hard.
so you can coast downhill.
to a gear that will cause your engine to exceed its redline.
3. A low air pressure warning signal is required on:
all vehicles with air brakes.
all vehicles with air brakes built after 2009.
all vehicles with air brakes built after 2005.
Warning signals are optional.
4. When the wheels of a trailer lock up:
ABS will increase stopping power.
the vehicle will gradually come to a complete stop.
the trailer will tend to swing around.
All of the above.
5. To use the controlled braking method in an emergency, you should:
apply the brakes as hard as you can without locking the wheels.
apply your brakes all the way, and release the brakes when the wheels lock up.
apply the brakes when the wheels lock up.
pump the brake pedal 3 times.
6. When the air system is fully-charged, the air loss rate for a single vehicle with the engine off should be less than:
3 psi in one minute.
2 psi in one minute.
4 psi in one minute.
2 psi in 30 seconds.
7. If the low pressure warning signal doesn't work:
this could cause sudden emergency braking in a single-circuit air system.
you could lose air pressure and you would know it.
in dual systems the stopping distance will be decreased.
None of the above.
8. Which of the following is NOT part of the drum brake?
Return spring
Brake drum
Safety valve
9. The spring brakes come on:
when you lose ABS control.
when air pressure in both air brake systems rises to a value set by the manufacturer.
when main air pressure is lost.
when you bring the vehicle to a complete stop right away.
10. Service brakes should:
always be checked before applying the brakes.
be checked before each trip.
only be checked by a mechanic.
All of the above.
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SC CDL Air Brakes Test

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