Abstract: A shock absorber assembly for mounting between a vehicle frame and wheel assembly including a cylinder containing a substantially incompressible fluid and a piston slidably mounted in the cylinder to divide it into two separate chambers on opposite sides of the piston. A hollow piston rod is connected to the piston at one end and extends out of one end of the cylinder, where it is mounted in a base assembly. A fluid flow passageway in the piston rod communicates between the two chambers. An adjustment rod slidably mounted in the piston rod controls the size of the fluid flow passageway. A biasing assembly acts between the piston and adjustment rods to urge them relative to one another so as to increase the size of the fluid flow passageway, allowing a degree of automatic adjustment to the compression and rebound rates of the assembly dependent on the prevailing road conditions.