The theory of side slip angle of tractor was already established by means of a Model Tractor, and the running characteristics pulling the load could be predicted for any tractor on the slope, testing only the adhesion and maximum resistance force of side slip.
But as it was not made sure with the real wheel tractor, a ordinary used two wheel tractor was tested for the poupose of verification of the theory. And the same time, the characters of side slip with the two kind of lug patterns were compared.