California CDL Air Brakes Practice Test

The California 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 (California does not publish its own number).

Last updated Oct 7, 2026. FirstTry CDL is a CDL permit test prep site by Hive Asset Group, LLC.

By Scott Wilder, Editor

Last reviewed against the California CDL manual on October 7, 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.

California CDL permit facts

What	What California says	Source
Air Brakes pass mark	At least 80%. This is the federal minimum (49 CFR 383.135); California does not publish its own number.	Official page
CLP fee	No separate CLP fee is listed. You pay the nonrefundable application fee ($100 for Class A or B, $59 for Class C commercial) when you apply, good for 12 months	Official page
CLP validity	Up to 180 days from issue. It can be renewed for another 180 days if the expiration is not more than one year from the first application date	Official page
CLP holding period	Hold the CLP at least 14 days before the skills test	Official page
Test languages	The DMV commercial handbook (2019 edition) says commercial knowledge tests are offered in English, Arabic, Chinese, Punjabi, Russian and Spanish. Skills tests must be done in English and interpreters are not allowed. No English-only rule for commercial knowledge tests was found on dmv.ca.gov as of October 2026.	Official page

20 question Air Brakes practice test

1. What can too much heat do to drum brakes?
1. A. Make them grab harder
2. B. Make them stop working
3. C. Raise the air pressure in the tanks
4. D. Make the shoes adjust themselves
Show answer
Answer: B. Make them stop working
Heat from hard or long braking can make the brakes stop working.
From the official CDL manual, section 5.1.8.
2. How may the parking brakes be controlled on older air brake vehicles?
1. A. By a lever
2. B. By a foot pedal only
3. C. By a steering wheel button
4. D. By the engine brake
Show answer
Answer: A. By a lever
On older vehicles, the parking brakes may be controlled by a lever.
From the official CDL manual, section 5.1.15.
3. What does the safety valve protect the air brake system from?
1. A. Too little pressure
2. B. Water in the tanks
3. C. Worn brake linings
4. D. Too much pressure
Show answer
Answer: D. Too much pressure
The safety valve protects the tank and the system from too much pressure.
From the official CDL manual, section 5.1.6.
4. Where is the ABS malfunction lamp on a trailer?
1. A. On the right side, at the front or rear corner
2. B. On the roof near the front of the trailer
3. C. On the left side, at the front or rear corner
4. D. On an instrument panel at the trailer front
Show answer
Answer: C. On the left side, at the front or rear corner
Trailer ABS lamps are yellow and sit on the left side at a front or rear corner.
From the official CDL manual, section 5.1.16.
5. What happens if your air brakes are not adjusted properly?
1. A. Only the regular brakes are affected
2. B. Only the parking brakes are affected
3. C. Nothing, spring brakes work without adjustment
4. D. Neither the regular nor the parking brakes will work right
Show answer
Answer: D. Neither the regular nor the parking brakes will work right
The braking power of spring brakes depends on the brakes being in adjustment.
From the official CDL manual, section 5.1.14.
6. What do you look for on the air hoses connected to the brake chambers?
1. A. Paint chips
2. B. Bright colors
3. C. Extra length
4. D. Cuts or wear from rubbing
Show answer
Answer: D. Cuts or wear from rubbing
The manual says to make sure the hoses are not cut or worn from rubbing.
From the official CDL manual, section 5.3.2.
7. How do you test the parking brake in the final air brake check?
1. A. Set it and gently pull against it in a high gear
2. B. Set it and rev the engine with the transmission in neutral
3. C. Release it and tap the brake pedal at 20 mph
4. D. Set it and gently pull against it in a low gear
Show answer
Answer: D. Set it and gently pull against it in a low gear
You put the parking brake on and gently pull against it in a low gear to see that it holds.
From the official CDL manual, section 5.3.3.
8. How do you test the low air pressure warning signal?
1. A. Run the engine and watch for the signal at fast idle
2. B. Engine off, power on, then fan the brake pedal to lower pressure
3. C. Open all tank drain valves with the engine running
4. D. Pull the parking brake knob out and wait for the signal
Show answer
Answer: B. Engine off, power on, then fan the brake pedal to lower pressure
You shut the engine off, turn the electrical power on, and step on and off the brake pedal to bring pressure down.
From the official CDL manual, section 5.3.3.
9. What causes brakes to fade or fail?
1. A. Too much engine braking on a downgrade
2. B. Air tank pressure that is too high
3. C. Leaving the parking brake off overnight
4. D. Too much heat from overusing the brakes instead of using engine braking
Show answer
Answer: D. Too much heat from overusing the brakes instead of using engine braking
Brakes fade or fail from excessive heat caused by using them too much and not relying on the engine braking effect.
From the official CDL manual, section 5.4.5.
10. Which pair shows the typical pressures where the compressor starts and stops pumping?
1. A. Starts at about 100 psi, stops at about 125 psi
2. B. Starts at about 85 psi, stops at about 100 psi
3. C. Starts at about 125 psi, stops at about 100 psi
4. D. Starts at about 20 psi, stops at about 45 psi
Show answer
Answer: A. Starts at about 100 psi, stops at about 125 psi
The manual says pumping should start at about 100 psi and stop at about 125 psi (check manufacturer's specifications).
From the official CDL manual, section 5.3.3.
11. Where is the safety relief valve installed?
1. A. In the first tank the compressor pumps air to
2. B. In the last tank at the end of the system
3. C. Next to the brake pedal in the cab
4. D. In each of the brake chambers at the wheels
Show answer
Answer: A. In the first tank the compressor pumps air to
The valve sits in the first tank the compressor fills.
From the official CDL manual, section 5.1.6.
12. Which vehicles may have a front brake limiting valve control in the cab?
1. A. Some older vehicles made before 1975
2. B. All vehicles made after 1997
3. C. Only buses that carry passengers
4. D. Only trailers pulled by tractors
Show answer
Answer: A. Some older vehicles made before 1975
Some vehicles made before 1975 have the cab control marked normal and slippery.
From the official CDL manual, section 5.1.13.
13. The low air warning has come on during your check. How do you continue to test the spring brakes?
1. A. Restart the engine and build pressure to 125 psi
2. B. Push the parking brake knob in and drive forward
3. C. Keep stepping on and off the brake pedal to lower pressure more
4. D. Open the drain valves on the wet tank
Show answer
Answer: C. Keep stepping on and off the brake pedal to lower pressure more
You keep fanning the brake pedal to reduce tank pressure until the spring brakes come on.
From the official CDL manual, section 5.3.3.
14. When may a driver fully apply the brakes in an emergency stop with ABS?
1. A. Whenever only the tractor has ABS
2. B. Whenever only the trailer has ABS
3. C. Whenever the road is dry
4. D. When driving a straight truck or combination with working ABS on all axles
Show answer
Answer: D. When driving a straight truck or combination with working ABS on all axles
The one exception is a driver who always drives vehicles with working ABS on all axles, who can fully apply the brakes in an emergency stop.
From the official CDL manual, section 5.4.2.
15. What is the controlled braking method?
1. A. Pressing the pedal all the way, then releasing when the wheels lock
2. B. Tapping the pedal lightly many times in a row
3. C. Braking as hard as you can without locking the wheels
4. D. Using only the engine brake and the parking brake
Show answer
Answer: C. Braking as hard as you can without locking the wheels
In controlled braking you apply the brakes as hard as you can without locking the wheels.
From the official CDL manual, section 5.4.3.
16. You pull hard on a slack adjuster. Movement of more than what distance at the push rod means it probably needs adjusting?
1. A. About one quarter inch
2. B. About one inch
3. C. About three inches
4. D. About six inches
Show answer
Answer: B. About one inch
A slack adjuster that moves more than about one inch where the push rod attaches probably needs adjustment.
From the official CDL manual, section 5.3.2.
17. How does the air compressor get its power?
1. A. An electric motor runs it from the battery
2. B. Gears or a v-belt connect it to the engine
3. C. The air pressure in the tanks turns it
4. D. The brake pedal drives it
Show answer
Answer: B. Gears or a v-belt connect it to the engine
The compressor is driven by the engine through gears or a v-belt.
From the official CDL manual, section 5.1.1.
18. It starts to rain. Where should you set the front brake limiting valve control?
1. A. Normal
2. B. Slippery
3. C. Halfway between the two settings
4. D. Slippery, but only if there is ice
Show answer
Answer: A. Normal
The control should stay in normal for normal stopping power.
From the official CDL manual, section 5.1.13.
19. When is it acceptable to manually adjust an automatic slack adjuster?
1. A. Every morning as part of the pre-trip
2. B. Any time the brakes feel a little soft
3. C. Whenever the push rod stroke is past the limit, as a permanent fix
4. D. Only as a temporary fix in an emergency
Show answer
Answer: D. Only as a temporary fix in an emergency
Manual adjustment of an automatic adjuster is only a temporary measure for an emergency, because the real problem remains.
From the official CDL manual, section 5.3.2.
20. When you check brake drums, linings, and hoses, what must be true of the mechanical parts?
1. A. They must be painted
2. B. They must be in place and not broken or missing
3. C. They may be loose if they are clean
4. D. They may be missing if the brakes still work
Show answer
Answer: B. They must be in place and not broken or missing
The manual says mechanical parts must be in place, not broken or missing.
From the official CDL manual, section 5.3.2.

California CDL Air Brakes questions

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

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

Is the California 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. California uses its own handbook: https://www.dmv.ca.gov/web/eng_pdf/comlhdbk.pdf

How much does a CDL permit cost in California?

CLP fee: No separate CLP fee is listed. You pay the nonrefundable application fee ($100 for Class A or B, $59 for Class C commercial) when you apply, good for 12 months.

What languages is the California CDL knowledge test offered in?

The DMV commercial handbook (2019 edition) says commercial knowledge tests are offered in English, Arabic, Chinese, Punjabi, Russian and Spanish. Skills tests must be done in English and interpreters are not allowed. No English-only rule for commercial knowledge tests was found on dmv.ca.gov as of October 2026.

Sources

https://www.ecfr.gov/current/title-49/section-383.135
https://www.dmv.ca.gov/portal/driver-licenses-identification-cards/licensing-fees/
https://www.dmv.ca.gov/portal/driver-licenses-identification-cards/commercial-driver-licenses-cdl/
https://www.dmv.ca.gov/web/eng_pdf/comlhdbk.pdf
Manual sections used in this test: 5.1.1; 5.1.13; 5.1.14; 5.1.15; 5.1.16; 5.1.6; 5.1.8; 5.3.2; 5.3.3; 5.4.2; 5.4.3; 5.4.5

Air Brakes practice test in nearby states