Florida CDL Air Brakes Practice Test 2026
You must pass the Air Brakes test if the vehicle you will drive has air brakes, including air over hydraulic brakes. Without it, your CDL carries an air brake restriction. The material is Section 5 of the Florida CDL Handbook: the parts of an air brake system, dual systems, inspecting the system, and using the brakes.
Expect numbers on this test: pressure ranges, build-up times, leakage limits. Florida's manual sets some of them differently from other states, and these questions follow the Florida manual.
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Question 1 of 15
How often should air tanks with manual drain valves be drained?
Water and oil build up in air tanks during normal operation. If left to accumulate, this moisture can damage the braking system or freeze in cold weather and cause brake failure. Draining at the end of every driving day keeps the tanks clean and the brakes reliable.
Handbook: 5.1.4 - Air Tank Drains
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Question 2 of 15
When you push the brake pedal (treadle valve) farther down in an air brake vehicle:
Pressing the pedal deeper opens the treadle valve wider, allowing more compressed air to flow to the brake chambers. More air pressure means greater force pushing the brake shoes or pads against the drums or rotors, which increases stopping power.
Handbook: 5.1.7 - The Braking System
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Question 3 of 15
Why do air brake systems use multiple air storage tanks (reservoirs)?
If the compressor fails, the reservoirs act as a backup supply so you can still stop the vehicle safely more than once. Without that stored air, a single compressor failure could leave you with no braking ability at all.
Handbook: 5.1.3 - Air Storage Tanks
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Question 4 of 15
The final air brake pre-trip check is to test the service brake by:
This test checks whether the brakes apply evenly and respond properly under real conditions. Moving at 5 mph gives you enough motion to feel any pulling, lag, or unusual response without risking a collision if something is wrong.
Handbook: 5.3.3 - Test Service Brakes
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Question 5 of 15
Total stopping distance for a vehicle with air brakes is LONGER than for a car with hydraulic brakes primarily because:
Air brakes take extra time to work because air must travel through the lines before the brakes apply. This is called brake lag. Combined with the much greater weight of a truck, it takes significantly more distance to stop than a typical car.
Handbook: 2.6.1 - Stopping Distance
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Question 6 of 15
Slack adjusters on air brakes should be checked because:
Slack adjusters control how far the brake pushrod travels to apply the brakes. If a slack adjuster is out of adjustment, the brakes won't apply with full force, or may not apply at all. Automatic slack adjusters can still fall out of adjustment, so manual checks are required.
Handbook: 5.3.2 - Slack Adjusters
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Question 7 of 15
The supply pressure gauge in the cab of an air brake vehicle shows:
The supply pressure gauge tells you how much compressed air is stored in your tanks and ready to use. Watching this gauge lets you know if your air pressure drops dangerously low, which would affect your ability to brake safely.
Handbook: 5.1.10 - Supply Pressure Gauges
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Question 8 of 15
During a pre-trip inspection, cracks in brake drums:
Cracked brake drums can fail under the heat and stress of braking, which could cause a complete loss of braking on that wheel. A vehicle with cracked drums is considered out of service until repaired.
Handbook: 5.3.2 - Brake Drums or Rotors
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Question 9 of 15
The air compressor governor controls:
The governor sets the pressure range for the air brake system. It signals the compressor to stop pumping when tank pressure reaches the "cut-out" level (around 125 psi) and to start again when pressure drops to the "cut-in" level (around 100 psi).
Handbook: 5.1.2 - Air Compressor Governor
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Question 10 of 15
On long, steep downgrades, a driver's main way to control speed should be:
Gravity pulls a heavy vehicle faster and faster on a downgrade, and brakes alone will overheat and fade if used continuously. Selecting a low gear before the descent lets the engine slow the vehicle naturally, so the brakes only need short, firm applications to manage speed rather than constant pressure.
Handbook: 2.16.3 - Brake Fading or Failure
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Question 11 of 15
With the engine off and the brakes fully applied, the maximum allowable air leakage rate is:
These are the federal standards for acceptable air loss with a static (non-moving) system under full brake application. A single vehicle leaks less because it has fewer air lines and connections than a combination vehicle, which adds a trailer with its own lines and couplings.
Handbook: 5.3.3 - Test Air Leakage Rate
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Question 12 of 15
The air brake safety valve in the supply tank is usually set to open at:
The safety valve protects the air system from dangerous pressure buildup. It releases air automatically if the compressor fails to shut off, and 150 psi is the standard pressure at which it opens.
Handbook: 5.1.6 - Safety Valve
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Question 13 of 15
A low-air-pressure warning signal in an air brake vehicle must activate before pressure drops below what level?
The warning light or buzzer must kick in before tank pressure falls below 60 psi, giving you time to safely stop before losing braking ability. At 60 psi you still have enough pressure to brake, but below that the brakes may not work properly.
Handbook: 5.1.11 - Low Air Pressure Warning
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Question 14 of 15
What is the primary purpose of an air compressor in an air brake system?
The air compressor is the starting point of the whole system. It pumps air and stores it in tanks called reservoirs. That stored compressed air is what powers the brakes when you press the pedal.
Handbook: 5.1 - The Parts of an Air Brake System
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Question 15 of 15
In a dual air brake system, before driving you should allow the air pressure to build to at least:
Both the primary and secondary systems need at least 100 psi before you drive, so you have full braking power in an emergency. If you picked 60 psi, you are probably thinking of the low air pressure warning. In Florida that warning must come on before pressure falls below 55 psi, and it means stop and park safely, not that you are cleared to drive. Wait for both gauges to reach 100 psi before you release the parking brake. See handbook 5.2, Dual Air Brake.
Handbook: 5.2 - Dual Air Brake
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Download on the App StoreMore Florida CDL practice tests
- General Knowledge Practice TestTaken by every CDL applicant, whatever the license class.
- Combination Vehicles Practice TestRequired for a Class A license.
- Hazmat Practice TestH endorsement. Also needs a TSA background check.
- Passenger Practice TestP endorsement, for vehicles that carry 16 or more people.
- Tank Vehicles Practice TestN endorsement, for tanks over 119 gallons each and 1,000 combined.
- School Bus Practice TestS endorsement, for driving a school bus.
- Doubles and Triples Practice TestT endorsement, for pulling double or triple trailers.
- Road Signs PracticeSigns, signals and pavement markings, as a refresher.
Florida CDL Exam is an independent study aid. It is not affiliated with, endorsed by, or approved by the FLHSMV, the FMCSA, or any Department of Transportation. Questions are original, written from the public Florida CDL Handbook, and are not actual exam questions. Read the official Florida CDL Handbook (PDF).