| 摘要 |
PROBLEM TO BE SOLVED: To provide a pneumatic tire excellent in durability at its bead portions, advantageously inhibiting the fatigue breakage of the bead portions by improving the structure of bead cores for preventing the separation of a carcass ply at its wind-up ends. SOLUTION: At least one carcass ply formed out of steel cords has a carcass body 1 toroidally extended from a tread portion through sidewall portions to bead portions and wind-up portions 4 turned around bead cores embedded in the bead portions from inside to outside in a tire radial direction, with all or part thereof wound up along the peripheral face of the bead cores 3. The hexagonal contour of the cross section of the bead core 3 in a tire cross direction has a diameter in a tire radial direction, where the ratio of an insidemost diameter (a) in a tire cross direction to an outsidemost diameter (b) is 0.3<=b/a<1.0.
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