A tubular downhole tool string component having a sidewall with a fluid passageway formed therein between a first end and second end, and a valve mechanism disposed within the fluid passageway adapted to substantially cyclically build-up and release pressure within the fluid passageway such that a pressure build-up results in radial expansion of at least a portion of the sidewall and wherein a pressure release results in a radial contraction of the portion of the sidewall. The valve mechanism disposed within the fluid passageway comprises a spring. Radial expansion and contraction of the portion of the sidewall varies a weight loaded to a drill bit disposed at a drilling end of the drill string.