- Updated for January 2025
- Based on 2025 IA commercial driver's license manual
Free Iowa CDL Air Brakes Test 2025
Today, you will be taking a practice exam, based on information from the Iowa Commercial Driver License Manual, to prepare for the exam that will allow you to drive vehicles with air brakes. The questions have been written based closely on the kinds that you will find on the real DMV exam, so practice often, and pay close attention to the hints and explanations included. Reading them will help you prepare to answer questions in the future on your air brake exam. Keep studying, practice until you have a score you feel confident in, and keep driving safely!
- Perfect for first-time and renewal CDL/CLP applicants, and those adding endorsements
- Triple-checked for accuracy
What you need to know
What to expect on the actual IA DOT exam
questions
correct answers to pass
passing score
Helpful links
List of questions (classic view)
- How would you check your truck's slack adjusters?
- Which of the following will be true about your brake function if your anti-lock braking system (ABS) fails?
- Under which conditions are front wheel brakes good?
- Which vehicles must have low air pressure warning signals?
- Which of the following is NOT part of the drum brake?
- Which of the following can cause brakes to fail or fade?
- Which of the following should you do before leaving your vehicle unattended?
- When should you use the parking brake?
- The purpose of a supply pressure gauge is
- If the air tanks are not drained,
- Which of the following are true about a dual air brake system?
- Which of the following is NOT part of the air brake system?
- Slack adjusters are
- Which of the following is NOT part of the braking process when driving a tractor-trailer combination vehicle with an anti-lock braking system (ABS)?
- What is the best way to test if your vehicle's spring brakes come on automatically?
- The tractor protection valve
- How do brakes work on a long, steep downgrade?
- At what measurement is the safety valve USUALLY set to open?
- An anti-lock braking system (ABS)
- Spring brakes are
- Why must you study air brakes in the state of Iowa?
- What is the best way to test your vehicle's low air pressure warning signal?
- When should you drain your air tanks?
- How can you tell if your vehicle is equipped with an anti-lock braking system (ABS)?
- After the initial drop, the maximum acceptable leakage rates per minute are
- The low air pressure warning signal will come on before the pressure in the air tanks falls below
- A low pressure warning signal is required on
- All vehicles equipped with air brakes have
- With air brake-equipped vehicles, the parking brakes should be used
- The use of air brakes on a downgrade is only a supplement to the
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