| 摘要 |
PROBLEM TO BE SOLVED: To provide a run-flat tire having side reinforcement rubber layers with highly balanced run-flat durability and ride comfort at normal internal pressure. SOLUTION: In this pneumatic run-flat radial tire, the side reinforcement rubber layers are formed in an entire region of both sides along the inner face of a carcass ply 2. The carcass ply 2 has a mono-ply structure, and the number of cord overlapped joint portions of the carcass ply layer is smaller than two. A gap between positions of the cord overlapped joints of inner and outer layer sides of the carcass ply layer is 50 mm or longer in the tire circumferential direction. In the cord overlapped joint part of the carcass ply layer, four or more cords of the carcass ply 2 are not vertically overlapped. The cord of the carcass ply includes 50 mass% of PK fiber. The maximum heat shrinkage stress of the cord is 0.1 to 1.8 cN/dtex, and the heat shrinkage rate of the PK fiber at the time of dry heat treatment at 150°C for 30 minutes is 1 to 5%. COPYRIGHT: (C)2008,JPO&INPIT
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