How air brakes work
Air brake basics cover tank pressure, the three braking systems, and how air moves brake parts.
Your airThis gauge shows your supply pressure.Building pressureStart the engine and the compressor builds pressure. At about one twenty five the governor cuts out.Cut-inUse the brakes and pressure drops. Around one hundred psi the governor cuts back in and refills the tanks.
Lessons in this chapter
5 lessons, about 5 minutes each
- Reading the air brake pressure gauge Lesson 1 · free
- Three brake systems in one
- Compressor, governor and safety valve
- Keeping the air clean and dry
- Foundation brakes and slack adjusters
Built on CDL Manual (AAMVA 2025 CDL Testing System), Section 5 Air Brakes and 6.2 Combination Vehicle Air Brakes; 49 CFR 383.111(b) · March 2025 · 5.0 Air Brakes; 5.1 The Parts of an Air Brake System (5.1.1–5.1.10)
The full class, $19 at launch.
Paid once, when it opens. Lesson 1 is free now.
- Animated systems
- Your state’s manual numbers
- Practice tests that explain
Not affiliated with FMCSA or any state DMV. Check your state’s CDL manual.