and two depending parallel arms 48 through which the spring is bolted this structure is exemplary only it being clear that the clevis could be attached to the bracket 30 and rather than the arm 28 and other engineering variations are conceivable within the scope of the invention the spring action should be damped by one or more shock absorbers which perhaps ideally should parallel the spring however practical considerations of exposure to dirt and damage in off road conditions suggest that as illustrated at 50 the shock absorbers should be mounted between the swing arm and upper frame members such as seat supports 16 tests have indicated that the vertical shock forces in the undampened direction coupled to the frame by the shock absorbers especially when they are forwardly raked as shown in fig1 do not substantially interfere with the dynamic advantages provided by the improved spring means in keeping with the overall requirements that the spring means used be substantially horizontally reacting and connected to the frame below the operational center of gravity several other embodiments of the spring means is replaced by a compression spring 52 which is captured between two retaining caps 54 and 56 as best seen in fig5 cap 54 has welded thereto a pair of bars 58 of which extend through the hollow core of the spring and pass through slots 60 in retaining cap 56 and are pivotally connected at 62 to an arm or bracket 64 which extends downwardly from the lower member of the.