<div class="htmlview paragraph">Traction limits the capacity of a tractor and the traction device is usually the most inefficient element in the power train. This paper presents performance criteria of traction devices together with definitions of important terms. Facilities and techniques for evaluating tractive performance are briefly discussed and studies of different carcass constructions of rubber tractor tires, effects of tandemizing wheels, forces on an individual track shoe, contact pressures between a smooth tire and a firm soil, relative tread movement on a rigid surface, and the distribution of stresses in soil caused by a track and a rubber tire are presented.</div>