| 摘要 |
PURPOSE:To improve friction force against the ice and snow road surface in particular by forming block patterns on the tread surface, and by specifying tread developing width and the groove area ratio to the tread surface respectively and also by forming a tread section of specific foaming rubber having closed cells therein. CONSTITUTION:A plurality of blocks 3 are formed on the tread surface 10 surrounded by a plurality of main grooves 1 extending in the tire peripheral direction E-E' and a plurality of cross grooves 2 extending in the tire cross direction. In this case, tread developing width TDW is to be set to 80% or more of maximum tire width, and the groove area ratio of the tread surface 10 to 30% through 45%. A tread section is formed of foaming rubber having closed cells therein. The foaming rubber is formed with urea-formaldehyde assistant of quantity less than foaming agent compounded in the foaming rubber compounded, and JIS hardness at a temperature of 10 deg.C is set to 60 through 74, the average foam area of the tread surface 10 to 500 through 4,000mum<2>, the coefficient of variation of each foaming area to 0.5 through 0.8, and foam occupation area to 10% through 35%. |
