| 摘要 |
PROBLEM TO BE SOLVED: To reduce the weight of a tire while insuring burst limit inner pressure equal to or more than the case of using steel wire by providing a bead core constituted by winding rubber coated polybenzazole fiber cord, and specifying thickness of coated rubber filling the adjoining gap of fiber cords. SOLUTION: A bead core 3 is formed with a thin rubber coated layer 6 on the outer circumferential face of a polybenzazole fiber cord 5, and the polybenzazole fiber cord with rubber coated layer 7 is wound into required step number and row number so as to be an inner diameter size meeted with the diameter of an applied rim utilizing adhesiveness of the rubber coated layer 6 to be formed. In the bead core 5 of a product tire, thickness of coated rubber filling the adjoining gap of the mutual polybenzazole fiber cords 5 is favorably set to be at least 0.001 mm and under 0.2 mm. Hereby the weight of a tire can be effectively reduced, the burst limit pressure of the bead part can be effectively improved, and the durability of the bead part can be improved.
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