🎧 25 audio-narrated practice questions

Air Brakes CDL Practice — Pass the 25-Question Test

Air Brakes is 25 questions — and it is the #1 reason new drivers fail on test day.

Practice all 25 Air Brakes topics with audio narration. Leak-down tests, stopping distances, low-air warnings.

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Why Air Brakes is tricky

Air brake systems are mechanical and unforgiving. The test mixes component identification, procedure sequences, and regulatory numbers like '90 psi', '60 psi', '55 psi' that all sound alike under pressure.

4 study moves that actually work

1
Memorize the four warning pressures first: 60 psi (low-air warning), 20-45 psi (parking brakes apply), 90-100 psi (cut-out), 100-125 psi (cut-in).
2
The leak-down test sequence is high-yield: fully charged, engine off, brakes released = 2 psi per minute max. Brakes applied = 3 psi per minute max.
3
Practice the 'applied pressure test' with audio mode — it is a sequence you will repeat on every pre-trip for your career.
4
Learn the difference between service brakes, parking brakes, and emergency brakes. Questions mix these terms on purpose.

CDL sections

Audio

parked-study review

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What you get in the Koydo CDL app

🎧

Audio for every question

All 25 Air Brakes questions narrated for parked or off-road study.

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Adaptive review

Missed questions resurface until you get them right twice.

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FAQ — Air Brakes

Can I drive any CDL vehicle without the Air Brakes test?

No. If the test vehicle you take the skills test in has air brakes, you must pass the Air Brakes knowledge test. Failing it puts an 'L' restriction on your CDL limiting you to vehicles without air brakes.

Is Air Brakes part of General Knowledge or separate?

Separate. Air Brakes is a standalone 25-question knowledge test. You take General Knowledge + Air Brakes + whatever endorsements you need.

How does Koydo CDL help with Air Brakes specifically?

All 25 Air Brakes questions include audio narration and a diagram-style explanation for the component identification items that are otherwise hard to memorize on a written study guide.

Other CDL sections

General Knowledge →Combination Vehicles →Hazardous Materials →Doubles and Triples →Tanker Vehicles →Passenger Transport →School Bus →Pre-Trip Inspection →

Ready to pass Air Brakes?

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4 study moves that actually work

Memorize the four warning pressures first: 60 psi (low-air warning), 20-45 psi (parking brakes apply), 90-100 psi (cut-out), 100-125 psi (cut-in).

The leak-down test sequence is high-yield: fully charged, engine off, brakes released = 2 psi per minute max. Brakes applied = 3 psi per minute max.

Practice the 'applied pressure test' with audio mode — it is a sequence you will repeat on every pre-trip for your career.