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Air Brakes Practice Question 54

Restriction L if not passedAir Brakes · Question 54

Wedge brake actuators differ from S-cam brakes in that they:

• AUse a wedge driven by a pushrod to spread the brake shoes
• BHave no slack adjuster
• CApply only the parking brake
• DAre pneumatic-electric hybrids

Correct answer: A. Use a wedge driven by a pushrod to spread the brake shoes

Why: Wedge brakes are an alternative actuation that pushes a wedge between the brake shoes. They are self-adjusting and have no manual slack adjuster.

How this question fits the Air Brakes test

An air brake failure on a loaded combination vehicle can cause runaway, jackknife, or fire. The CDL Air Brakes test exists because air systems behave very differently from hydraulic brakes — drivers must understand pressure build, air loss tolerance, and stopping distance under load.

Study technique for this topic

Memorize the seven steps of the air brake pre-trip check, the leak-down rates for single and combination vehicles, the warning signal pressure threshold, and the spring brake automatic application pressure range. Practice the order of operations — never rely on muscle memory in the booth.

Related Air Brakes practice questions

• Q35. When you make an emergency stop in a vehicle with ABS, you should:
• Q48. A safety valve on the supply tank typically vents at approximately:
• Q62. After applying brakes during a stop, you should:
• Q13. The trailer hand valve (trolley valve, Johnson bar) should be used:
• Q26. If the ABS warning light stays on after start-up:

Continue your CDL preparation

The Air Brakes portion of the CDL knowledge exam covers more than this single question. Use this site's full Air Brakes bank to drill every topic, then test yourself with one of our state-specific practice sets to confirm you are ready for the actual DMV exam in your state. Always check your state's CDL handbook for any local addenda before the test day.

If you are still building your overall CDL foundation, start with the General Knowledge bank — every CDL applicant must pass it — and then work outward to the endorsements you plan to add.