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Free South Carolina (SC) CDL Air Brakes practice test 2026

The section applicants fail most often. Pressure figures differ by state manual.

What’s different in South Carolina

Most Air Brakes questions are the same federal material in every state. One question in the app is written for South Carolina alone, from the South Carolina Commercial Driver's License Manual (2025 CDL Testing System, Version March 2025).

Low air warning on the written air brakes test: Before pressure drops below 60 psi. The national model manual says 55 psi.South Carolina manual, section 5.1.4
Low air warning in the pre-trip inspection (skills test): Before pressure drops below 55 psi.South Carolina's CDL manual and licensing pages
Skills test version: The modernized skills test.South Carolina's CDL manual and licensing pages

A South Carolina question, answer shown

Under the South Carolina manual, the visible warning for low air pressure must appear before the tanks fall below what pressure?

60 psi(correct answer)
80 psi
45 psi
55 psi

The manual used in South Carolina sets the visible low air pressure warning at 60 psi, higher than the 55 psi in the AAMVA model manual. Older vehicles may use one half the governor cut-out pressure instead.

Handbook section 5.1.4

Practice every South Carolina Air Brakes question

A sample question

One example, answer shown. Practicing the rest happens in the app.

At approximately what pressure does the air compressor governor stop pumping air into the tanks?

125 psi(correct answer)
150 psi
100 psi
60 psi

The governor 'cut-out' pressure is about 125 psi. When tank pressure falls to roughly 100 psi, the governor cuts back in and the compressor resumes pumping.

Handbook section 5.1.2

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