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Air Brakes Practice Question 55

Restriction L if not passedAir Brakes · Question 55

A glad hand seal that is cracked or missing will:

• AImprove coupling
• BCause an air leak between tractor and trailer
• CLock the brakes on
• DActivate ABS

Correct answer: B. Cause an air leak between tractor and trailer

Why: Glad hand seals (rubber grommets) make the air-tight connection at the coupling. Cracked or missing seals cause air loss and prevent proper brake function.

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

• Q5. Spring brakes typically apply automatically when air pressure falls to approximately:
• Q18. When checking manual slack adjuster travel, the rule of thumb is the chamber pushrod shoul…
• Q31. When parking on a downgrade, the front wheels should be turned:
• Q44. When uncoupling, before disconnecting the air lines you should:
• Q58. When the trailer service brake glad hand becomes disconnected, the trailer brakes will:

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.