| 摘要 |
PURPOSE: To provide a pneumatic radial tire for a small passenger car which does not deteriorate the breaking strength of the tire and has an improved driving stability. CONSTITUTION: This pneumatic radial tire for a small passenger car is not more than 13 inches in size and its bead core of a bead portion comprises a mono-strand formed by helically winding and binding the wires of a circular section covered with rubber. The lap length L (mm) of the start of winding and the end of winding satisfies the relationship expressed by the equation L>=4.0×10×πr<2> (f/A) (where r is a radius of the wire, f is tensile strength of the wire (kgf/mm<2> ) and A is pulling force of the wire from covered rubber (kgf)) and the sectional shape of the bead core forms a regular hexagon with a fine structure comrising 7 wires along the circumference of not less than 80% of the whole circumference and the wire is 1.25-1.55mm in diameter (D).
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