| 摘要 |
PURPOSE:To improve the heat resisting property, cut and chip resisting property of a radial tire by disposing an undertread compound in a specified position while setting the loss tangent, thickness, etc., of said compound respectively to a specified ratio of a cap tread compound. CONSTITUTION:A belt layer 2 is disposed between a carcass layer 3 and a cap tread compound 1 in a tread portion. Then, an under tread compound 5 is disposed in the section of tire inside a phantom extension a drawn from the widthwise end of the outermost belt layer 23 in a shoulder region T/4 parallel to tread radius in the direction of side portion 7. And the loss tangent of compound 5 is made smaller than that of compound 1 and the elastic modules of compound 5 is 0.6-0.9 times that of compound 1. Also, the thickness of compound 5 is 2.0-8.0 times that Hc of a single layer in the belt layer 2 of substantial reinforcing member.
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