| 摘要 |
PURPOSE: To prevent the occurrence of separation between a belt and a carcass as well as the propagation thereof by providing the carcass and a belt layer at the prescribed cord angle with a tire equatorial surface, and applying the preset value to the porosity and total strength of the belt and cord with the intermediate line of the carcass kept to the prescribed form. CONSTITUTION: An organic fiber carcass 16 having two or more bead cores 12 and 14, and a cord angle between 25 and 45 degrees with tire equatorial surface is provided, and a belt layer 20 made of of two or more layers of intersecting cords is laid outside the carcass 16 in a radial direction at cord angles between 15 and 25 degrees with the surface. Provided that the radius of curvature of the shoulder section of a carcass intermediate line L is taken at R, and an angle formed with a normal line TL from a tread side end point T to the line L, and a segment ST between the end S of the widest belt layer 22 and the point T isθ, a relationship of 0.001<tanθ/R<0.004 is established and the end S is positioned inside the normal line TL. Also, the porosity of a belt and cord is taken at a value between 35 and 50%, and total strength per belt layer at a value between 4,000 and 7,500kg. According to this construction, separation between a belt 20 and a carcass 16 as well as the propagation thereof can be prevented at a stage after an intermediate travel period.
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