Abstract: A frame unit for a vehicle having a main frame unit adapted to support the main body of the vehicle comprising a pair of structural side members and a structural cross-piece member defining an integral extension unit having an H-shaped configuration, such extension unit including means disposed at the intersections of the side members and the cross-piece member and on rearwardly disposed sections of the side members for securing the extension unit to the main frame unit of the vehicle whereby sections of the side members extend forwardly to the main frame unit and are disposed in a crumple zone of the vehicle.