A caster assembly for a wheelchair comprises a stem having a frame clamp at a first end and a fork clamp at a second end, the frame clamp configured to form a frame joint with at least one rotational degree of freedom with a frame portion of the wheelchair, a tightening of the frame clamp securing the stem to the frame portion, the frame joint having a frame rotational axis. A fork unit has a fork portion and a caster rotatably supported by the fork portion, the fork unit having swivel mechanism, and a joint portion forming a rotational joint with the fork clamp of the stem, a tightening of the fork clamp blocking rotation of the rotational joint, the rotational joint having a fork rotational axis. A vector of the fork rotational axis is normal to a fork rotational plane in which the fork rotates relative to the stem, and further wherein the frame rotational axis is not parallel to the fork rotational plane.
