The steering arm has a head (9) at a sideways offset to the axis of rotation (13) of the driven wheel (6). The edge of the head nearest the outside of the truck is at a closer distance to the axis of rotation of the driven wheel than the inside edge of the head is to the axis of rotation of the driven wheel. The distance between the outside edge of the head and an adjacent wall is increased. This space is available for turning of the steering arm to manoeuvre the truck without the arm projecting beyond the edge of the truck.
