As system pressure keeps falling with the engine off and brakes released, in what range do the spring brake control valves usually pop out and apply the spring brakes?

• A.Between about 120 and 125 psi
• B.Only at exactly 0 psi
• C.Between about 90 and 100 psi
• D.Between about 20 and 45 psi

Why

Spring brakes are designed to apply automatically as pressure falls through roughly the 20 to 45 psi range. Waiting for that to happen while driving means you have ignored the low-air warning for far too long.

Manual topic: Air Brakes - Spring Brakes · From the General Knowledge practice bank (GK-108).

Practice this subject as a full test

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