| 摘要 |
A pneumatic radial tire has a double crown structure that an annular recess portion is arranged in a tread at a given region in a widthwise direction thereof, in which the tread is divided into a central region, a pair of middle regions and a pair of side regions and at least one auxiliary reinforcing cord layer is arranged on a belt so as to substantially envelop a crown portion of a carcass and a full radially outer surface of the belt, provided that a stretching ratio of the cords in the auxiliary reinforcing cord layer in the central region and side regions is equal to or more than that in the middle regions, whereby high-speed durability is improved together with excellent drainage while controlling the increase of tire weight and cost as much as possible.
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