This paper will focus on three case study examples of commercial vehicle wheel end fires that were caused by operating the vehicles with the parking brakes applied. Because it analyzes the most commonly utilized conventional air/drum brake systems in the US market, this analysis is applicable to most heavy duty trucks, tractors, semi-trailers, and buses equipped with air drum brake systems and dual wheel/tire combinations at the wheel ends. This paper will outline and illustrate the vehicle components analyzed, the typical fire patterns observed, and the methodologies used to help determine the correct origin, and when to correctly relate the cause of the fire to the operation of the vehicle with the parking brakes applied. The case studies include a 6×4 tractor equipped with two parking brake chambers, a 6×4 tractor with four parking brake chambers, and a single axle semi-trailer with two parking brake chambers.