A vehicle frame that includes first and second frame portions. The first frame portion has a plurality of struts associated with each other to form a first framework. The second frame portion is associable with the first frame portion in a stiffening association for significantly increasing the stiffness of the first frame portion. The associated first and second frame portions are configured to support a rider sitting on the vehicle frame. The associated frame portions also define an interior cavity dimension for housing a component of the propulsion system for propelling the vehicle. The associated frame portions also comprise attachments for supportedly connecting two wheels of the vehicle, a seat disposed on the frame, and other vehicle accessories and systems.