TotalTruckParts.net, HowStuffWorks.com and SuspensionSpecialists.com are some websites that provide air brake system diagrams and schematics. Some of the diagrams are available for viewing online, and others can be downloaded as a PDF.
TotalTruckParts.net, a truck driving resource site, offers diagrams for the typical six-wheel air brake system and the typical 10-wheel air brake system. Each diagram includes a color key for identifying air valves and lines.
The auto section of HowStuffWorks.com supplies an article that uses an air brake diagram to illustrate how air brakes work. Maintenance and repair tips are included.
SuspensionSpecialists.com provides air brake system diagrams and schematics in air brake trouble shooting charts and handbooks available for download in PDF format, as of 2015.