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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 Iowa CDL knowledge test. The IA 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 Iowa CDL Manual. Take this IA CDL practice test now to prepare for the actual air brakes test!
1. You should always try to back toward the driver's side because:
backing toward the left side is more dangerous.
you can watch the rear of your vehicle out the side window.
None of the above.
2. If your vehicle does not have automatic air tank drains, how often should you drain air tanks to remove moisture and oil?
Once a week.
At the end of each working day.
Every 4 hours.
3. The ________ brake system applies and releases the brakes when the driver uses the brake pedal during normal driving.
4. In some vehicles a modulating control valve may be used to:
apply the spring brakes gradually.
decrease the pressure in the brake system.
apply the front brakes.
5. The stop light switch:
turns on the brake lights when you put on the air brakes.
tells you when you need to use your parking brake instead of the service brake.
warns you when the air supply pressure drops below 55 psi.
6. Stepping on and off the brake pedal several times:
reduces the air pressure in the tanks.
may cause air leaks.
may result in dangerously thin linings.
7. Vehicles with air brake systems take longer to come to a complete stop than vehicles with hydraulic brakes because of:
brake lag.
brake fading.
reaction distance.
8. Overloading a vehicle with cargo can have negative effects on all of the following except:
Weight limits
9. What should you do to correct a drive-wheel braking 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.
Turn in the same direction as the skid.
10. When you pull hard on a slack adjuster and it moves more than about _____ where the push rod attaches to it, the slack adjuster probably needs adjustment.
1/2 inch
2 inches
1 inch
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IA Air Brakes Test

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