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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 Idaho CDL knowledge test. The ID 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 Idaho CDL Manual. Take this ID CDL practice test now to prepare for the actual air brakes test!
1. What is the best way to test the low air pressure warning signal?
step on and off the brake pedal while the engine is running.
Shut the engine off when you have enough air pressure, turn the electrical power on and step on and off the brake pedal to reduce air pressure to below 60 psi.
pump the brakes until the air pressure drops below 45 psi.
2. The Johnson bar is a valve that:
reduces the braking pressure to a safe level.
is installed in the first tank the air compressor pumps air to.
works the trailer brakes.
3. The low pressure warning signal will generally activate when the air pressure falls between:
55–75 psi.
80–85 psi.
85–100 psi.
4. Rough acceleration:
improves gas mileage.
is necessary to warm up the engine.
can cause mechanical damage.
5. When you release the brake pedal, the _____ rotates back and a spring pulls the brake shoes away from the drum.
pressure gauge
air compressor belt
6. How do you test hydraulic brakes for leaks?
Pull forward against parking brake to make sure the hydraulic brakes holds.
Pump the brake pedal three times, then apply firm pressure to the pedal and hold for five seconds. The pedal should not move.
Pump the brake pedal ten times and see if it holds.
7. Tar in the road pavement rising to the road surface in very hot weather:
is very sticky and will slow down your vehicle.
causes the road to become very slippery.
does not affect the road surface or driving conditions.
8. If air doesn't flow all the way to the back:
your brakes will not work properly.
a rollover is more likely.
the trailer will tend to swing around.
9. What should you do to test your vehicle's low air pressure warning signal?
Pump the brakes until the air pressure drops below 80 psi.
With the engine running, put the vehicle in a forward gear and attempt to drive forward.
With the key in the "on" or "battery charge" position, rapidly apply and release the foot brake.
10. Axle weight is:
the maximum safe weight your tires can carry at a specified pressure.
the weight transmitted to the ground by one axle or one set of axles.
the weight of all the axles added together.
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ID Air Brakes CDL Test

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