of front or a set of rear wheel and tire combinations 56 of a vehicle 58 the rod like support member and two channel members are designed for easy space saving storage and for portability also in both of the aforementioned embodiments the proximal end 32 of the cross member 30 may be extended radially outwardly in a direction opposite to that of distal end 34 of cross member 30 and have mounted on this opposite distal end portion a counter balancing means of selected weight this weight serves to offset the weight of the rider and to facilitate rotation of the swing about the central support in the alternative the opposite distal end portion may support a swing in operation of the preferred embodiment a rider sits in seat 42 and grasps flexible supporting members 44 the rider repeatedly thrusts his legs forwardly and then retracts them in a conventional 34 pumping 34 style thereby causing the swing seat to move forwardly and backwardly as the rider continues to surge his body the swing 40 gains momentum and amplitude and cross bar 30 moves through a series of increasing arcs about the longitudinal axis of bearing device 20 finally cross.