It is, however, well known that the dispersion of silica in the rubbery matrix is not as good as that of carbon black, which was regarded to be one of the reasons for its inferior ability of reinforcement. In situ sol-gel reaction of alkoxysilane in rubber, on the other hand, has been recognized as a novel method for improving the dispersion of particulate silica in the rubbery matrix.[9-16] The silica thus produced is called, “in situ silica”. Use of silane coupling agents is one way to improve silica dispersion, but the additional component may have complicated the composite system.