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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 Indiana CDL knowledge test. The IN 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 Indiana CDL Manual. Take this IN CDL practice test now to prepare for the actual air brakes test!
1. What factors can cause brakes to fade?
Dirt roads and in unpaved yards.
Slippery surfaces and shaded areas.
Gravel and tar.
Excessive heat and brakes out of adjustment.
2. You are driving on a steep downgrade. If your safe speed is 35 mph, you should apply the brakes when your speed reaches:
35 mph
45 mph
25 mph
30 mph
3. If the safety relief valve in the air brake system releases air:
the valve is fully operational.
this will supply more power to the drive wheels.
something is wrong.
this will supply more power to the brakes.
4. With the controlled braking method, you:
apply the brakes all the way and release brakes when the wheels the lock up.
apply the brakes as hard as you can without locking the wheels.
push down on the brake pedal as hard as you can so that the wheels the lock up.
None of the above.
5. If stopped on a hill, how can you start moving without rolling back?
Partly engage the clutch before you take your right foot off the brake, put on the parking brake if necessary.
Press on the gas pedal, even if you have to roll back a little.
Release the parking brake before you have applied enough engine power to keep from rolling back.
None of the above.
6. When you make a quick lane change, the crack-the-whip effect can:
the trailer to swing wide to the left.
turn the trailer over.
make it harder to turn without skidding.
improve your traction.
7. When parking a trailer without spring brakes, it is very important for safety that you use wheel chocks. Why?
You may not notice a major leak in the service line until you try to put the brakes on.
if you don't use wheel chocks, supply air will be sent to the service line instead of going to charge the trailer air tanks.
The air could leak out of the trailer air tank, releasing its emergency brakes.
None of the above.
8. How should you apply the brakes when going down a steep downgrade?
Apply the brakes when you reach the bottom of the downgrade.
You should not brake, and only use engine braking to prevent brake failure.
Apply the brakes whenever you reach your safe speed, until your speed has been reduced to 5 mph below your safe speed.
Apply the brakes as hard as you can without locking the wheels.
9. What should you do to correct a drive-wheel braking skid?
Turn in the same direction as the skid.
Fully apply the brakes, turn the steering wheel quickly, push in the clutch, and countersteer.
Stop braking, turn the steering wheel quickly, push in the clutch, and countersteer.
None of the above.
10. The use of air brakes on a steep downgrade is only a supplement to:
the braking effect of the engine.
the use of the spring brakes.
the use of the parking brakes.
the use of the "controlled braking" method.
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IN Air Brakes CDL Test

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