Seven mathematical models for the interaction of a pneumatic tire with a roadway are analyzed. This study involves a single-wheel trailer, and it is assumed that the tire and roadway touch each other at only one point. Results of numerical solutions of equations of motion are given in graphical form for the first four models. Significant disparities are found among the predictions of the various theories. This work is intended to form the basis for experiments to be performed to determine which model, if any, is, in fact, valid.