| 摘要 |
PURPOSE:To improve wet property by arranging a main groove to be provided on a tread into a continuous groove and by gradually increasing a crossed angle by the tangent of the main groove and a tyre equatorial face and a cross area of the main groove from the starting point of the main groove to the terminal and specifying the main groove pitch at the tread end. CONSTITUTION:Main grooves 16, 17 are provided, while being slid by 1/2 pitches in the circumferential direction, on the first and the second treads 13, 14. A crossed angle A by the tangent L of this main grooves 16, 17 and the equatorial face 12 of a tyre is gradually increased from the starting points 16a, 17a of the main grooves 16, 17 to terminals 16b, 17b which opens to a tread end and set to 0 deg.-60 deg.. And the pitches P of the main grooves 16, 17 at the tread ends 18, 19 are set to 0.2-1.0 times a tread width W. And the cross areas of the main grooves 16, 17 too are gradually increased from the starting point to the terminal. By this constitution, the permeation of water into between a tyre tread and a road is restrained and the earth contact area of the tyre can be increased and wet property can be improved. |
