Supply side
An engine-driven compressor supplies air to the system. An air dryer removes moisture and contaminants before the air is stored in reservoirs (tanks).
Keeping the supply side healthy helps protect valves and chambers further down the line, which is why dryer maintenance is part of routine service.
Control side
Valves route and modulate air when the driver applies the brakes. Relay valves, quick-release valves and the foot valve each have a defined role, and replacements must match the original specification.
Foundation brakes
Brake chambers convert air pressure into mechanical force. On drum brakes this force moves a slack adjuster and camshaft; on air disc brakes it acts through a caliper.
Brakes are safety-critical. Inspection, adjustment and replacement should follow the vehicle manufacturer's documentation and be carried out by a qualified technician.
General information only. Always follow the vehicle and component manufacturer's documentation, and have safety-critical work carried out by a qualified technician.