A seat suspension system for use on a tractor or the like including an air bag means for resiliently supporting a seat and a shock absorber positioned generally vertically but at an incline between the seat and a base frame and functioning to dampen the vertical oscillation of the seat. The shock absorber is pivotably supported to permit variation in its inclination and consequent variation in its damping effect on the relative vertical motion of the seat. A readily accessible adjusting means is provided for changing the relative inclination of the shock absorber and includes a pivotable bellcrank positioned beneath the front portion of the seat and having one lever arm connected to the upper end of the shock absorber. The other lever arm of the bellcrank is accessible to the tractor operator to permit pivotal movement of the bellcrank.