Questions on Real Exam
25
Air Brakes — DL-7C
Minimum to Pass
20 Correct
80% passing threshold
Practice Questions
30
Full module coverage
Test Order
Step 3 of 4
After Special Requirements
Quick Reference — Texas DL-7C
Handbook Section
DL-7C Section 5
Real Exam Questions
25 questions
Minimum to Pass
20 correct (80%)
Practice Questions
30 questions
Normal PSI Range
100–125 PSI
Low Air Warning
Activates at 60 PSI or before
The Air Brakes test is only required if your CDL vehicle has an air brake system. Passing it removes the air brake restriction from your CDL. Study Section 5 of the DL-7C carefully. The pre-trip inspection sequence (LAB test), spring brake activation pressure (20-45 PSI), and brake fade prevention are the most frequently tested topics on the Texas Air Brakes exam.
What the Texas CDL Air Brakes Test Covers
The real Texas CDL Air Brakes exam has 25 questions, and you need 20 correct (80%) to pass. Topics tested include:
- Air brake system components and controls
- Dual air systems
- Pre-trip air brake inspection
- Air pressure and brake fade
- Spring brakes
- Emergency braking
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Texas CDL Air Brakes Practice Questions
Texas CDL Air Brakes — Complete Study Guide
The Air Brakes test is required for any CDL applicant whose vehicle has an air brake system. Passing it removes the air brake restriction from your Texas CDL — allowing you to legally operate vehicles equipped with air brakes. The test is based on Section 5 of the Texas CDL Handbook (DL-7C) and has 25 questions on the real exam. You need 20 correct (80%) to pass. FastLessonHub provides 30 practice questions covering every testable topic in Section 5.
Most Tested Air Brakes Topics: The spring brake activation range (20-45 PSI), low air pressure warning activation point (at or before 60 PSI), acceptable pressure drop in leak tests (max 3 PSI/min for single vehicles, 4 PSI/min for combinations), and the correct downgrade gear selection rule appear on almost every Texas Air Brakes exam.
Key Topics Covered
- Air Brake System Components — Air compressor, storage tanks, safety valve (opens at ~150 PSI), drain valves (drain daily), foot valve (treadle valve), brake chambers, S-cam, slack adjusters, and push rods. Understanding what each component does is essential.
- Air Pressure Ranges — Normal operating range: 100-125 PSI. Low air warning: activates at 60 PSI or before. Spring brakes apply: 20-45 PSI. Safety valve opens: approximately 150 PSI. Governor cut-in: ~100 PSI. Governor cut-out: ~120-125 PSI.
- Spring Brakes — Spring brakes are held in the released position by air pressure. When pressure drops to 20-45 PSI, the spring automatically applies the brakes — this is the fail-safe design. The yellow diamond knob in the cab controls the tractor spring brakes; the red octagon controls the trailer spring brakes.
- Pre-Trip LAB Test — L = Leaks: with engine off and brakes applied, pressure should not drop more than 3 PSI/minute for single vehicles (4 PSI for combinations). A = Application: low air warning must activate before 60 PSI; spring brakes must apply at 20-45 PSI. B = Build-up: pressure should build from 85 to 100 PSI within 45 seconds at idle.
- Brake Fade Prevention — Select the correct low gear before starting a downgrade — the same gear you would use climbing that grade going uphill. Use engine braking as primary speed control. Use snub braking (apply firmly then release) rather than continuous brake application. Never ride the brakes continuously on a downgrade.
- Dual Air Systems — Dual air systems have two independent circuits — primary and secondary. If one circuit fails, the other maintains partial braking. The low air warning activates for the failed circuit. Both circuits must be at or above 60 PSI before driving.
- ABS and Emergency Braking — With ABS: apply firm continuous brake pressure and hold — do NOT pump the brakes. ABS modulates pressure automatically. Without ABS: use threshold braking (maximum pressure just short of wheel lockup). Stab braking is an alternative for non-ABS vehicles.
- Brake Lag — Air brake systems have a lag of approximately one-half second between pressing the pedal and brakes applying. At 55 mph, this equals approximately 40 feet of unbraked travel. This is why CMVs require greater following distances than passenger vehicles.
Key Numbers to Know
25
Questions on real exam
20
Correct to pass (80%)
30
Practice questions here
100-125
Normal PSI range
60 PSI
Low air warning threshold
20-45
Spring brake activation PSI
150 PSI
Safety valve opens at
3 PSI
Max leak rate/min (single)
4 PSI
Max leak rate/min (combo)
45 sec
Pressure build-up test
½ sec
Brake lag time
40 ft
Distance during brake lag at 55 mph
Frequently Asked Questions
What is the Texas CDL Air Brakes test?
The Air Brakes test is a Texas CDL knowledge exam based on Section 5 of the DL-7C handbook. It has 25 questions and requires 20 correct (80%) to pass. It is required for any CDL applicant whose test vehicle has an air brake system. Passing removes the air brake restriction from your Texas CDL.
At what PSI do spring brakes automatically apply?
Spring brakes automatically apply when air pressure drops between 20 and 45 PSI. Spring brakes are held in the released position by air pressure — when pressure drops too low to hold the powerful spring back, the spring applies the brakes automatically. This is a fail-safe design that ensures a vehicle with total air failure will stop rather than roll away.
What is the LAB test for Texas CDL air brakes?
LAB stands for Leaks, Application, and Build-up. The Leaks test checks that pressure does not drop more than 3 PSI per minute (single vehicles) or 4 PSI per minute (combinations) with brakes applied. The Application test verifies the low air warning activates before 60 PSI and spring brakes apply at 20-45 PSI. The Build-up test confirms pressure builds from 85 to 100 PSI within 45 seconds.
What causes brake fade on a Texas CDL downgrade?
Brake fade occurs when continuous brake application generates excessive heat in the brake drums and linings, reducing friction and braking effectiveness. Prevention requires selecting the correct low gear before the descent, using engine braking as the primary speed control, and using snub braking (apply firmly then fully release) rather than continuous partial application.
What is brake lag and why does it matter?
Brake lag is the delay of approximately one-half second between pressing the brake pedal and the air reaching the brake chambers to apply the brakes. At 55 mph, this equals approximately 40 feet of unbraked travel before stopping begins. This is one reason CMVs need greater following distances than passenger vehicles — brake lag is added to perception distance and reaction distance to create total stopping distance.