bogie
n.— «The non-steering wheels in front of the “bogies” are called “pusher axles” and wheels behind the “bogies” are called “tag axles.” They are single wheels. And they are for wieght regulations. If there are three drive axles in a row they are called a “tridem” instead of “bogie.”» —“Fabulous Peterbilt rigids. Biglorryblog shows the pride of Paccar!” Big Lorry Blog (United Kingdom) Feb. 20, 2008. (source: Double-Tongued Dictionary)