CDL · Air Brake Inspection

During an air brake check, you should know that air pressure should build from 85 to 100 psi within what timeframe?

Reviewed by Jordan Morley, Editorial Lead at 247SimpleTests. Written by the 247SimpleTests Editorial Team from the official source material cited on every question.

Correct answer

Within about 45 seconds for dual air systems (build-up rate test)

A Within 10 minutes
B Within about 45 seconds for dual air systems (build-up rate test)
C Within 45 seconds
D It doesn't matter

Why this is the answer

In a typical AIR PRESSURE BUILD-UP test for dual air systems, pressure should build from 85 to 100 psi within about 45 seconds. CDL air brakes pre-trip. This checks that the compressor is building air at an adequate rate. If pressure builds too slowly, the system may not maintain adequate air during operation (a safety concern). The pre-trip air brake test also includes checking the low-pressure warning, the spring brake activation point, and testing for air leaks (the system shouldn't lose more than a set amount of pressure per minute). Knowing the build-up rate test is commonly tested.

Source: FMCSA CDL Manual — Air Brakes, Build-Up Rate

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About this topic: Air Brake Inspection

Air brake inspection is its own structured procedure: build-up, leakage rate, low-air warning, and spring-brake activation must all check out before you drive. This is one of 13 Air Brakes questions on air brake inspection, each with a full explanation on a single study page.

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During an air brake check, you should know that air pressure should build from 85 to 100 psi within what timeframe?

Why this is the answer

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About this topic: Air Brake Inspection

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