A simple genetic algorithms (GAs) has been applied to generate the optimum pitch sequence. Though a simple GAs worked properly, there was the problem of the premature convergence. To solve this problem, we introduced the new operator named the growth and combined it with a simple GAs. The growth operator, which is a kind of the hillclimbing technique, has the function to get the local optimum in a small CPU time.The GA with growth generated better sequence than a simple GAs. The GA with growth was verified not to have the premature convergence even in the smaller population size. The optimum pitch sequence generated by the GA with growth improved the noise performance such as pass-by noise compared with the current pitch sequence.

A new approach to determine an optimum tire contour was developed and was applied to improve various tire performances following the corresponding objective function and constraints. Although several tire contour theories have been proposed in the past, some of them were based on a simple model and could not be used to improve tire performances effectively. On the other hand, others were not described by an equation and their application was limited. In the new approach, the optimization technology was applied to efficiently obtain the optimum contour by minimizing an objective function, while satisfying the constraints. The new approach was verified to be able to improve various tire performances.

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A new optimization procedure to design the surface shape of tire patterns is proposed in which the optimality criteria is combined with finite element method. The effectiveness of this new procedure to control tread-element contact pressure distribution was verified by building and testing the rubber block samples. The objective function was the pressure uniformity on the block and the constraint was to keep the contact area in the optimization process. The shape of the optimized surface was round at the edges and concave at the center where the pressure was large in the flat surface block. The pressure of the block with the optimized surface became uniform and the friction coefficient increased 10% on dry compared with the flat surface block. Furthermore, this procedure was applied to complicated block shapes such as tire patterns and it was verified that the optimized surface effectively improved vehicle handling, riding comfort and irregular wear.