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Ontario Class A Practice Test · Question

Scenario 123: Spring (parking) brakes on a tractor-trailer will automatically apply when air pressure drops to about:

Spring brakes apply automatically as air pressure falls between roughly 20 and 45 psi, depending on the system. The correct answer is "20–45 psi". This capacity

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Question: Scenario 123: Spring (parking) brakes on a tractor-trailer will automatically apply when air pressure drops to about:

Answer options: ✅ 20–45 psi

  • 50–60 psi
  • 70–85 psi
  • 100 psi

Correct answer: 20–45 psi

Explanation: Spring brakes apply automatically as air pressure falls between roughly 20 and 45 psi, depending on the system. The correct answer is "20–45 psi". This capacity-fill scenario 123 reinforces the same competency for the class1 bank and follows the certified explanation standard.

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