| 摘要 |
PURPOSE:To improve every characteristic inherent in a tire, by making the cord occupying efficiency of a crown part constitute the specified carcass with a specific cord in diameter, twisting coefficient, elasticity and twisting numbers, in case of a radial-ply tire having a polyester carcass. CONSTITUTION:A polyester carcass is made up of the following elements that a diameter of a polyester cord is in a range of 0.75-1.30mm., a twisting coefficient alpha shown in the specified expression (see illustration) is larger than 0.36 but less than 0.60, elasticity epsilon in time of 2.25g/d is more than 3.3% but less than 6.0%, and a twisting number N of two or three polyester cords, while a cord occupying rate a/b measured in a tire circumferential direction of a crown center part is specified to a range of 30-50%. With this constitution, those of lightweightiness, low fuel consumability, high-speed resistance, drivability and vibro-rideability are all improvable. |
