| 摘要 |
PURPOSE:To raise operational stability furthermore without lowering a rolling resistance and durability during high-speed travelling, in the case of raising the operational stability by regulating the hardness of rubber of an under tread layer. CONSTITUTION:In a pneumatic radial tire having a tread part comprising an outside cap tread layer 4 and an inside under tread layer 3, the under tread layer 3 is formed of rubber in the center part 3c, the ratio of whose width to the ground contact width of the tire is in a range from 0.3 to 0.5, and rubber in the shoulder parts 3s connected to the both sides of the center part 3c. The JIS-A hardness of rubber of the center part 3c at 24 deg.C is set in a range from 70 to 80 and the JIS-A hardness of rubber of the shoulder parts 3s at 24 deg.C is set in a range from 50 to 60. |
