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The objective of this paper is to enhance the accuracy of tire model combined tire cornering and braking forces with anisotropic tread and carcass stiffness. The difference of tire longitudinal slip stiffness and cornering stiffness will arouse that the direction of tire resultant shear stress in adhesion region is not the same as that in sliding region. Then the direction of total friction force in the whole tire-road contact patch will change under different combined cornering/braking situations. Generally speaking, there is a basic premise: “the direction of resultant shear stress in sliding region will be the same as that in adhesion region” in the existing tire models, in which the anisotropy of tread and carcass stiffness is neglected. Therefore, these models don't work well when the tire tread and carcass stiffness has a strong anisotropy.

This paper focuses on the modeling process of incorporating inflation pressure into the UniTire model for pure cornering. Via observing and manipulating the tire experimental data, the effects of inflation pressure on the tire cornering property are analyzed in detail, including the impacts on cornering stiffness, the peak friction coefficient, the curvature of transition region and the pneumatic trail. And the brief mechanism explanations are also given for some of these impacts. The results show that some effects of inflation pressure are similar to that of vertical load on the non-dimensional tire cornering property, and there are strong interactive effects between the two operating conditions. Therefore, in order to obtain concise expressions, the inflation pressure is incorporated into the UniTire tire model by analogy with the expressions for vertical load, and the interactive effects are also taken into account.

The tire mechanics characteristics are essential for analysis, simulation and control of vehicle dynamics. This paper develops the UniTire model for tire forces and moments under combined slip conditions with anisotropic tire slip stiffness. The anisotropy of tire slip stiffness, which means the difference of tire longitudinal slip stiffness and cornering stiffness, will cause that the direction of tire resultant shear stress in adhesion region is different from that in sliding region. Eventually the tire forces and moments under combined slip conditions will be influenced obviously. The author has proposed a “direction factor” before to modify the direction of resultant force in the tire-road contact patch, which can describe tire forces at cornering/braking combination accurately. However, the aligning moments which are very complicated under combined slip conditions are not considered in previous analysis.