| 摘要 |
PROBLEM TO BE SOLVED: To provide a pneumatic radial tire which gives enhanced steering stability and riding comfort by adopting a belt layer consisting of Aramid fiber cords, or organic fiber cords, which enable weight reduction in comparison with the case of steel cords. SOLUTION: In a pneumatic radial tire, in which two belt layers 4d, 4u are provided on the outer peripheral side of a carcass layer 2, the belt layer 4d, the first one from the carcass layer 2, is formed with steel cords, while the belt layer 4u, the second one, is formed with polyethylene-2,6-naphthalate system fiber cords. In this case, the total denier D of this polyethylene-2,6- naphthalate system fiber cords should be 2000 to 6000. In addition, the twist coefficient K(=T√D), which is obtained from the total denier (number) D and the number or twists T per 100 mm of the cord, should be 500 to 1500. Moreover, the ratio of the number of final twists to the first twists should be 1.00 to 1.60.
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