Abstract: A torsion bar suspension system for a trailer that includes a suspension frame having a spindle at one end for rotatably carrying a wheel. The suspension frame is mounted to the trailer frame to pivot about an axis spaced from the wheel axis of rotation. A torsion bar is mounted to the trailer frame between the wheel end of the suspension frame and the suspension frame pivot axis. The torsion bar is operatively coupled to the suspension frame such that torque at the torsion bar resists pivoting of the suspension frame about its pivot axis. The torsion bar/suspension frame coupling comprises an arm of variable length to accommodate changing radius between the torsion bar and the suspension frame as the frame rotates about its pivot axis. The torsion bar and suspension frame are mountable and demountable to and from the trailer frame as an assembly. The suspension frame includes facility for adjusting height, camber and toe-in of the wheel.