| 摘要 |
PROBLEM TO BE SOLVED: To provide a light pneumatic radial tire capable of keeping high spped durability while suppressing separation between a cord and rubber in a circumferential belt layer or occurrence of break of the cord. SOLUTION: A gradient belt layer 20A provides in-surface bending rigidity for a tread part 16, and the tread part can endure a transverse force during cornering. The circumferential belt layer 20B including an organic fiber cord 21 substantially parallel to a tire equator surface CL provides circumferential rigidity for the tread part 16 to hold inner pressure and provides high high-speed durability. Circumferential residual tension of the tire per width 5 cm of the circumferential belt layer 20B is set from 45 kgf to 400 kgf, so that radial growth during high speed rotation is smaller, standing wave occurrence speed is also suppressed, a good effect is given to high speed durability of the tire, the separation between the organic fiber cord 21 and the coating rubber or the break of the organic fiber cord 21 due to long usage can be suppressed.
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