When transporting tens of thousands of pounds of weight in a semi truck, one of the most important components of that vehicle is the brakes. In heavy-duty trucks, buses and tractor trailers, the braking system consists of a compressor, air reservoir, governor, brake valve, foot pedal, brake chamber & slack adjuster. Since air is plentiful but hydraulic fluid could get lost in a leak, semi trucks rely on air-powered brakes to keep drivers and everyone else on the road safe. Learn how air brake systems function and how to troubleshoot, service and maintain air brake systems.