Abstract: The present invention provides a method for producing a rubber composition for tire tread, which is prepared by mixing 100 parts by mass of a rubber component containing 60 to 80 parts by mass of a natural rubber and 20 to 40 parts by mass of a modified conjugated dienic polymer having one or more functional groups having another atom than carbon and hydrogen, and 40 to 60 parts by mass of carbon black having a nitrogen adsorption specific surface area (N2SA) of 40 to 95 m2/g and a hydrogen release rate of 0.37% by mass or more based on 100 parts by mass of the rubber component, wherein the temperature of the rubber composition at the time of discharge in the kneading step for mixing carbon black therein is 170° C. or higher, a rubber composition obtained according to the production method, and a tire using the rubber composition.

Abstract: In a pneumatic tire for heavy load in which a rubber chafer 8 is disposed at least in a part brought into contact with a rim in a bead part 1, the rubber chafer uses a rubber composition which comprises 45 to 55 parts by mass of butadiene base rubbers containing 10 to 30 parts by mass of a syndiotactic 1,2-structure-containing polybutadiene rubber and 45 to 55 parts by mass of a natural rubber as a rubber component and more than 50 parts by mass and less than 60 parts by mass of carbon black having DBP of 85 to 115 ml/100 g and a specific surface area by nitrogen adsorption (N2SA) of 50 to 100 m2/g based on 100 parts by mass of the rubber component.

Abstract: In a pneumatic tire for heavy load in which a rubber chafer 8 is disposed at least in a part brought into contact with a rim in a bead part 1, the rubber chafer uses a rubber composition which comprises 45 to 55 parts by mass of butadiene base rubbers containing 10 to 30 parts by mass of a syndiotactic 1,2-structure-containing polybutadiene rubber and 45 to 55 parts by mass of a natural rubber as a rubber component and more than 50 parts by mass and less than 60 parts by mass of carbon black having DBP of 85 to 115 ml/100 g and a specific surface area by nitrogen adsorption (N2SA) of 50 to 100 m2/g based on 100 parts by mass of the rubber component.