Abstract: An apparatus for preloading a torsion bar includes an adjuster arm that is adapted to be attached to and extend radially from a torsion bar and includes a free end with an involute surface formed thereon. An adjustment nut is adapted to be rigidly attached to a support member for the torsion bar adjacent a free end of the adjuster arm. An adjustment bolt having a free end for engaging the involute surface of the adjuster arm is threadably engaged in the adjustment nut. When the adjuster arm is attached to the torsion bar and the adjustment nut is attached to the support member, rotation of the adjustment bolt rotates the adjuster arm and the torsion bar about a longitudinal axis of the torsion bar thereby changing a preload applied to the torsion bar. The adjustment bolt remains perpendicular to the involute surface while the adjuster arm rotates.