| 摘要 |
PROBLEM TO BE SOLVED: To improve riding comfort by constituting a tread part of a rubber composition to specify proportion of a dynamic elastic modules and a loss tangent provided by a small deformation visco-elasticity test at 20 deg.C. SOLUTION: A tread 3 is constituted of a rubber composition whose proportion E'/tanδof a dynamic elastic module E' and a loss tangentδprovided by a small deformation visco-elasticity test at 20 deg.C is 25-125MPa at the time of 10Hz excitation and 125-250MPa at the time of 1000Hz excitation. In the case when the tread 3 is constituted of two layers of an under tread on the side of a belt layer 6 and a cap tread on the side of a tread surface 7, at least the cap tread is constituted of this rubber composition. In this way, the proportion E'/tanδ(10Hz) is reduced and the proportion E'/tanδ(1000Hz) is increased to reduce both of tire passing noise at the time of coasting travelling and tire passing noise at the time of accelerated travelling.
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