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The tires are one of the most important parts of the vehicle chassis, as they significantly influence aspects such as vehicle's directional stability, braking performance, ride comfort, NVH, and fuel consumption. The tires are also a part whose size affects the vehicle's essential specifications such as wheelbase and track width. The size of the tires should therefore be determined in the initial stage of vehicle development, taking into account whether the size allows the vehicle to achieve the targeted overall performance. In estimations of vehicle performance, computer simulation plays more of an important role, and simulated tire models are designed to reproduce the measured tire characteristics of existing tires. But to estimate the chassis performance with various tire sizes or with tires of uncommon sizes, the prevailing modeling approach, “individual models for individual tires,” would not function well because of limited ability to expand tire models to unfamiliar sizes.

Various deformation shapes of the vehicle body were investigated for the purpose to establish vehicle body's performance criteria which correlates well to handling performance and ride comfort. Using evaluations by experienced test driver, the fact that the rigidity of each body deformation correlated well to different dynamic performance was found. With careful verification test, simple lateral frequency response was chosen as the criteria for handling performance and vertical response was chosen for ride comfort. These were applied to the development of our recent production vehicle body. Finite element analysis simulation with these criteria helped to make new construction to meet body performance targets with minimum weight during planning-stage of the development. Also, the targets of ride comfort and handling performance of actual vehicle were accomplished with very little structural change during the testing and improvement stage of the vehicle development.