CDL Air Brakes Practice Test Guide: Pass Your Endorsement in 2025
If you’re planning to drive a commercial vehicle equipped with air brakes, you’ll need to pass the Air Brakes Knowledge Test. This endorsement removes the air brakes restriction from your CDL and ensures you’re qualified to handle the unique requirements of air brake systems. In this comprehensive guide, you’ll find everything you need to know—from air brake components to test format and practice questions—so you can pass your test confidently and drive safely.
What Is the CDL Air Brakes Endorsement?
The Air Brakes Endorsement is not technically an endorsement but a restriction removal. If you take the skills test in a vehicle with air brakes and pass the air brake knowledge test, you will not have the “L” restriction on your CDL, which prohibits you from driving vehicles with air brake systems.
Who Needs the Air Brakes Test?
- Drivers seeking a Class A, B, or C CDL operating vehicles with air brakes
- Drivers testing in a vehicle equipped with air brakes
- School bus or commercial fleet drivers using air-braked vehicles
CDL Air Brakes Test Overview
| Test Format | Total Questions | Passing Score |
|---|---|---|
| Multiple Choice | 25–30 questions | 80% (typically 20–24 correct) |
The test is based on Section 5 of your state’s CDL manual and focuses exclusively on air brake system operations and safety.
Topics Covered on the Air Brakes Test
- Basic air brake system components
- Dual air brake systems
- Brake lag, fade, and adjustment
- Air brake inspection procedures
- Low pressure warning signals
- Spring brakes and emergency braking
- Air tank drainage and moisture management
- Compressor and governor operation
- Proper brake usage on downgrades
Sample CDL Air Brakes Questions
- What happens when the air pressure drops below 60 psi in a dual system?
- What is the purpose of the spring brakes?
- When should air tanks be drained?
- How can you check for air leakage?
- What should the air pressure build-up rate be during an engine test?
How to Prepare for the CDL Air Brakes Test
1. Study Section 5 of the CDL Manual
Section 5 is all about air brakes. Study it thoroughly and take notes. Pay close attention to system parts, braking techniques, and emergency responses.
2. Take Online Practice Tests
Websites like DMVExamPractice.com provide multiple sets of air brakes quizzes that mimic the real DMV test.
3. Watch Visual Tutorials
YouTube and CDL training schools offer video lessons demonstrating brake components, proper usage, and inspection steps. These are helpful for visual learners.
4. Attend a CDL Training Program
Professional CDL schools give hands-on instruction on how to inspect, test, and safely operate air brakes under real-world conditions.
Practical Air Brakes Skills Test
During the vehicle inspection and road test portion of your CDL skills exam, you must demonstrate a proper air brakes system check. This includes:
- Leak rate test
- Low air warning device test
- Emergency spring brake activation
- Compressor cut-in and cut-out test
- Brake application and pedal feel check
Common Mistakes to Avoid
- Forgetting to drain tanks daily
- Misunderstanding brake lag time
- Confusing service vs. emergency brakes
- Neglecting to check low-pressure warning systems
- Overusing service brakes on long downgrades
Requirements and Fees
- Must have a CDL or be applying for one
- Must pass a DOT physical and vision test
- State fees range from $10 to $40
- Air brakes test is usually part of a bundled skills exam
Benefits of the Air Brakes Endorsement
- Access to more CDL driving jobs
- Higher earning potential
- Increased confidence handling heavy-duty vehicles
- Ability to operate school buses, trucks, and coaches with air brakes
Test Day Tips
- Arrive early with all required documents
- Read questions slowly and completely
- Use logic and eliminate wrong answers
- Watch out for tricky wording like “always” or “never”
- Use the full time allotted—don’t rush
Conclusion
The CDL Air Brakes test is a vital step in becoming a professional commercial driver. Whether you’re upgrading your license or preparing for your first job in trucking, mastering air brake systems ensures you operate your vehicle legally and safely. Use this guide to prepare thoroughly, practice often, and approach test day with confidence. With proper study and hands-on training, you’ll be on your way to a successful career behind the wheel.