6 bolster spring 30 is known in the art and is preferably of the type distributed under the trade name hmx bolster spring kit by hendrickson international truck suspension systems located in woodridge ill but other similarly constructed bolster springs could also be used mounting bracket 32 includes anchor plate 27 which is adapted to be clamped over leaf spring 14 with u bolts 26 end 29 of mounting bracket 34 is adapted to be attached to frame member 16 with bolts 44 as best shown in fig2 mounting brackets 32 34 are adapted such that bolster assembly 28 may be mounted over axle 12 between frame member 16 and leaf spring 14 with separator plates 38 positioned essentially vertically and bolster spring 30 extending toward mounting bracket 18 and upwardly from axle 12 or generally diagonally between mounting bracket 32 and mounting bracket 34 the angle of separator plates 38 with respect to vertical affects the resulting ride and jounce control of the vehicle as the plates approach the vertical the ride becomes smoother but jounce is controlled less and the carrying capacity decreases as the plates deviate from the vertical jounce is controlled more and carrying capacity increases but the ride becomes less smooth in the preferred embodiment for a class 7 chassis plates 38 are positioned between approximately 5 u00b0 and 25 u00b0 from the.