Ohio CDL Air Brakes Practice Test

The Ohio CDL Air Brakes test is a multiple-choice knowledge test you take for your commercial learner's permit. You need at least 80% to pass. That's the federal minimum in 49 CFR 383.135 (Ohio does not publish its own number).

Last updated Oct 15, 2026. FirstTry CDL is a CDL permit test prep site by Hive Asset Group, LLC.

By Scott Wilder, Editor

Last reviewed against the Ohio CDL manual on October 15, 2026

Scott Wilder on X | scottwilderhq.com

FirstTry CDL is a CDL permit test prep site by Hive Asset Group, LLC. It offers free exam-style practice tests built from the official CDL manual. FirstTry CDL is not affiliated with any DMV, FMCSA or government agency. Practice questions are exam-style questions built from the official CDL manual, not actual test questions.

Ohio CDL permit facts

What	What Ohio says	Source
Air Brakes pass mark	At least 80%. This is the federal minimum (49 CFR 383.135); Ohio does not publish its own number.	Official page
CLP fee	$31.50 (listed as the CDL temporary permit fee, driver fee included)	Official page
CLP validity	12 months	Official page
Test languages	Drivers must read, speak and write English well enough to talk with the public, understand highway signs and answer official questions. Translation aids are not allowed. The BMV offers the CDL manual in English (HSY 7605) and Spanish (HSY 7606). Tests are taken in person at a driver exam station.	Official page

20 question Air Brakes practice test

1. How may an air compressor be cooled?
1. A. By air or by the engine cooling system
2. B. By the brake fluid only
3. C. By the air tanks only
4. D. By the governor
Show answer
Answer: A. By air or by the engine cooling system
The compressor may be air cooled or cooled by the engine cooling system.
From the official CDL manual, section 5.1.1.
2. In stab braking, what happens if you re-apply the brakes before the wheels start rolling?
1. A. The vehicle will not straighten out
2. B. The brakes work better
3. C. The spring brakes come on
4. D. The brake lag goes away
Show answer
Answer: A. The vehicle will not straighten out
Re-applying the brakes before the wheels start rolling keeps the vehicle from straightening out.
From the official CDL manual, section 5.4.3.
3. Using the proper downgrade technique, about how long should each brake application last?
1. A. About one second
2. B. About three seconds
3. C. About ten seconds
4. D. Until you reach the bottom of the grade
Show answer
Answer: B. About three seconds
The manual says each application should last about three seconds.
From the official CDL manual, section 5.4.6.
4. Your safe speed on a downgrade is 40 mph. You brake when you reach 40 mph. At what speed do you release the brakes?
1. A. 39 mph
2. B. 30 mph
3. C. 20 mph
4. D. 35 mph
Show answer
Answer: D. 35 mph
The manual's example slows from the 40 mph safe speed to 35 mph, about five mph below, then releases.
From the official CDL manual, section 5.4.6.
5. An older trailer may have ABS but it is hard to tell. What can you look for under the vehicle?
1. A. The electronic control unit and wheel speed sensor wires
2. B. A second air compressor
3. C. An alcohol evaporator
4. D. A front brake limiting valve
Show answer
Answer: A. The electronic control unit and wheel speed sensor wires
Look for the electronic control unit (ECU) and wheel speed sensor wires from the back of the brakes.
From the official CDL manual, section 5.1.16.
6. At 55 mph, with an average driver, good traction, and good brakes, total air brake stopping distance is about how far?
1. A. Over 450 feet
2. B. About 100 feet
3. C. About 200 feet
4. D. About 300 feet
Show answer
Answer: A. Over 450 feet
The manual says the total stopping distance at 55 mph under good conditions is over 450 feet.
From the official CDL manual, section 5.4.4.
7. Which type of foundation brake is the most common?
1. A. The s-cam drum brake
2. B. The wedge brake
3. C. The air disc brake
4. D. The hydraulic drum brake
Show answer
Answer: A. The s-cam drum brake
The s-cam drum brake is the most common foundation brake.
From the official CDL manual, section 5.1.8.
8. The low pressure warning does not work on a single-circuit air system. What could happen?
1. A. You could lose air without knowing, then get sudden emergency braking
2. B. The compressor would stop building air
3. C. The service brakes would apply more gently
4. D. The governor would cut out at 100 psi
Show answer
Answer: A. You could lose air without knowing, then get sudden emergency braking
Without a warning you would not know pressure is falling, and a single-circuit system could suddenly apply emergency braking.
From the official CDL manual, section 5.3.3.
9. Your truck has an alcohol evaporator and manual drain valves. Can you skip draining the tanks?
1. A. Yes, the alcohol clears water from the tanks
2. B. Yes, if you refill the alcohol container
3. C. No, you must still drain water and oil every day
4. D. No, but only once a week
Show answer
Answer: C. No, you must still drain water and oil every day
Alcohol does not remove water and oil, so daily draining is still needed with manual drains.
From the official CDL manual, section 5.1.5.
10. Typically, what is the pressure of a fully charged air system at the start of the leakage test?
1. A. 125 psi
2. B. 60 psi
3. C. 85 psi
4. D. 45 psi
Show answer
Answer: A. 125 psi
The manual says a fully charged system is typically 125 psi.
From the official CDL manual, section 5.3.3.
11. Why is the s-cam called an s-cam?
1. A. It stands for steel cam
2. B. It stands for safety cam
3. C. It was named after its inventor
4. D. It is shaped like the letter S
Show answer
Answer: D. It is shaped like the letter S
The s-cam is named because it is shaped like the letter S.
From the official CDL manual, section 5.1.8.
12. What is brake lag?
1. A. The time it takes you to see a hazard
2. B. The time it takes you to move your foot to the pedal
3. C. The time it takes for the brakes to work after you push the pedal
4. D. The distance the vehicle travels while the brakes are slowing it
Show answer
Answer: C. The time it takes for the brakes to work after you push the pedal
Brake lag is the time required for the brakes to work after the brake pedal is pushed.
From the official CDL manual, section 5.4.4.
13. For the air leakage test, you release the parking brake. How do you release it?
1. A. Push the valve in
2. B. Pull the valve out
3. C. Press the foot brake only
4. D. Turn off the compressor
Show answer
Answer: A. Push the valve in
The manual says to release the parking brake by pushing the valve in.
From the official CDL manual, section 5.3.3.
14. In the proper low gear on a downgrade, how hard should you apply the brakes?
1. A. Just hard enough to feel a definite slowdown
2. B. As hard as you can without locking the wheels
3. C. As lightly as possible, and keep them applied all the way down
4. D. Only enough to turn on the brake lights
Show answer
Answer: A. Just hard enough to feel a definite slowdown
The proper technique is to apply the brakes just hard enough to feel a definite slowdown.
From the official CDL manual, section 5.4.6.
15. What does the low air pressure warning usually look like?
1. A. A red light, and a buzzer may also sound
2. B. A yellow light that flashes on the mirror
3. C. A green light on the dash panel
4. D. A horn that sounds outside the cab
Show answer
Answer: A. A red light, and a buzzer may also sound
The warning is usually a red light, with a possible buzzer.
From the official CDL manual, section 5.1.11.
16. You have a modulating control valve. What happens when you move the lever farther?
1. A. The spring brakes come on more softly
2. B. The spring brakes release
3. C. The spring brakes come on harder
4. D. The air tanks drain
Show answer
Answer: C. The spring brakes come on harder
The more you move the control lever, the harder the spring brakes come on.
From the official CDL manual, section 5.1.15.
17. What is a dual air brake system?
1. A. One air system that uses two air compressors
2. B. Two complete sets of brake pedals and controls
3. C. Two separate systems with a single set of controls
4. D. A system with extra tanks for the trailer only
Show answer
Answer: C. Two separate systems with a single set of controls
A dual system has two separate air systems that are worked by a single set of controls.
From the official CDL manual, section 5.2.
18. How do spring brakes work while you are driving?
1. A. Springs apply the brakes whenever you press the pedal
2. B. Air pressure pushes the springs onto the shoes
3. C. A cable keeps the springs compressed
4. D. Air pressure holds powerful springs back
Show answer
Answer: D. Air pressure holds powerful springs back
Air pressure holds the springs back, and the springs apply the brakes if the air is removed.
From the official CDL manual, section 5.1.14.
19. The yellow ABS lamp stays on after the bulb check. What may it mean?
1. A. The brakes have overheated from hard use
2. B. All of your regular brakes have stopped working
3. C. The parking brake knob is still pulled out
4. D. You may have lost ABS control at one or more wheels
Show answer
Answer: D. You may have lost ABS control at one or more wheels
A lamp that stays on may mean ABS control is lost at one or more wheels.
From the official CDL manual, section 5.1.16.
20. A brake with an automatic adjuster is found out of adjustment. What does the manual recommend?
1. A. Take the vehicle to a repair facility as soon as possible
2. B. Adjust it by hand and treat the problem as fixed
3. C. Make a few hard stops so it adjusts itself
4. D. Ignore it unless the brake pedal feels soft
Show answer
Answer: A. Take the vehicle to a repair facility as soon as possible
An out-of-adjustment automatic adjuster points to a mechanical problem that a repair facility should correct.
From the official CDL manual, section 5.3.2.

Ohio CDL Air Brakes questions

What score do you need to pass the Ohio CDL Air Brakes test?

You need at least 80% to pass. That is the federal minimum in 49 CFR 383.135. Ohio does not publish its own number.

Is the Ohio CDL Air Brakes test the same as other states?

The Air Brakes test is built on the same federal knowledge standards in every state, so the topics match the CDL manual. Ohio uses its own handbook: https://dam.assets.ohio.gov/image/upload/publicsafety.ohio.gov/HSY7605.pdf

How much does a CDL permit cost in Ohio?

CLP fee: $31.50 (listed as the CDL temporary permit fee, driver fee included).

What languages is the Ohio CDL knowledge test offered in?

Drivers must read, speak and write English well enough to talk with the public, understand highway signs and answer official questions. Translation aids are not allowed. The BMV offers the CDL manual in English (HSY 7605) and Spanish (HSY 7606). Tests are taken in person at a driver exam station.

Sources

https://www.ecfr.gov/current/title-49/section-383.135
https://www.bmv.ohio.gov/doc-fees.aspx
https://www.bmv.ohio.gov/dl-cdl-classes.aspx
https://dam.assets.ohio.gov/image/upload/publicsafety.ohio.gov/HSY7605.pdf
Manual sections used in this test: 5.1.1; 5.1.11; 5.1.14; 5.1.15; 5.1.16; 5.1.5; 5.1.8; 5.2; 5.3.2; 5.3.3; 5.4.3; 5.4.4; 5.4.6

Air Brakes practice test in nearby states