Abstract: A self propelled irrigation system has a drive tower on which a drive wheel is mounted to a rotating member of a drive mechanism with an axis of the wheel obliquely angled relative to a drive axis of the rotating member such that the wheel is tilted out of a plane normal to the drive axis. A hub has its oppositely facing sides arranged to support the wheel in such an orientation, and may therefore be mounted between the drive mechanism and wheel of a conventional irrigation system in which the wheel and drive axes were previously coincident. The tilt of the wheel causes an intentional wobble under rotation of the hub so that the wheel's point of engagement with the ground wanders back and forth during repeated passage of the drive tower over a particular path, thereby reducing a rut forming or deepening tendency of the irrigation system.