PURPOSE: To aim at lowering the calorific value and enhancing the durability of the tread section of a high speed and large sized pneumatic tire for buses or the like, the tread section having a two layers structure, by specifying the compositions and post- vulcanization characteristics of an inner surface rubber, the post-vulcanization characteristics of the outer surface rubber layer and the rate of the outer surface layer with respect to the tread section.
CONSTITUTION: An inner surface rubber layer 2 is composed of, by weight parts with respect to 100pts.wt. of a rubber component, 30W95pts. of a natural rubber and/or a synthetic polyisoprene rubber, 5W70 pars of polybutadiene, styrene butadiene copolymer rubber containing more than 2.5pts.wt. of stylene butadiene coplymer, polybutadiene rubber in which more than one specific atomic groups are coupled to molecular chains by carbon-carbon coupling, and 25W60pts. of carbon black having an I2 absorption amount of more than 50g/kg, so than the storage elastic modulus at 100°C after vulcanization is set at a value more than 3MPa, and the loss tangent is set at a value less than 0.15. Further, an outer surface rubber 1 having the abovementioned characteristics are set at a value of 3MPaW8MPa and a value less than 0.25, respectively, is formed such than the ratio thereof with respect to the tread section is set at a value of 0.6W0.9. With this arrangement it is possible to aim at enhancing the durability of the tread section.
HIRAKAWA HIROSHI
AWANE TOMOHIRO
Next Patent: PNEUMATIC TIRE IMPROVED HIGH SPEED DURABILITY PERFORMANCE