The spring brakes used on the chambers in a straight truck will bring you to a stop when air pressure drops below ____ psi.
Answer: A
20
The spring brakes used on the chambers of a straight truck and tractor will activate below 45 psi, usually in the 20 to 30 psi range.
All choices
- A20
- B100
- C60
Why the other answers are wrong
B. 100
Choice B is wrong because 100 psi is above the activation range for spring brakes, which activate below 45 psi.
C. 60
Choice C is wrong because 60 psi is above the typical activation pressure range of 20 to 30 psi for spring brakes.
CDL Air Brakes Test Info
Questions on Exam
25
Passing Score
80%
Time Limit
Typically 30 minutes; varies by testing location
The Air Brakes test content is federally standardized, so this question applies in every state. Age limits, fees, and testing procedures do vary — check your state's CDL requirements.
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More CDL Air Brakes Practice Questions
- Which component of the air brake system cuts-in at 100 psi to allow the air compressor to run?
- The driver must be able to see a low air pressure warning which comes on before pressure in the service air tanks fall below ____ psi.
- The safety valve is set automatically when pressure is:
- Parking or emergency brakes of trucks and buses can be legally held on by ____ pressure.
- Why drain water from compressed air tanks?