sag wagon
 n.— «The cyclists said they carry about 10 pounds of weight with them when they ride. The rest of their equipment and belongings travel with Barrett in the support vehicle or “sag” wagon, as they call it.» —“Cyclists visit Waterville en route to Key West” by Doug Harlow Morning Sentinel (Waterville, Maine) Sept. 16, 2004. (source: Double-Tongued Dictionary)