Abstract: A haying machine has a frame on which is fixed an upright threaded spindle defining an upright axis. A nut is threaded on this spindle so that rotation of the nut on the spindle displaces it axially along the spindle. A rigid wheel support has one end fixed to the nut and another end defining a horizontal axis about which a wheel rotates. A spring assembly normally urges the wheel with the associated support nut into a predetermined angular position corresponding to straight-ahead travel of the haying machine on the spindle. In order to adjust the height of the wheel it is merely rotated in the appropriate direction about the spindle with its associated nut and support.