The simulation tests were conducted on a mathematical model of a machine for one-phase harvest of a bush willow hanging on the front three-point suspension unit. During one working tour this designed and tested machine cuts down willow shoots, minces them and passes onto the parallel transport vehicle. The model of machine underwent simulation tests in order to, among others, determine the influence of the machine onto the loading capacity of wheels of the tractor. Three machine positions were tested: transport position, machine leaning on soil, and operational position during the cut-down of willow shoots. In these positions we calculated the pressing force of tractor wheels on the ground. The pressing forces were compared and the forces increased when the machine was in the cut-down position.