Base tread rubber composition

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Provided is a rubber composition for base tread which can improve steering stability, rolling resistance and durability without deteriorating extrusion processability, comprising 1.8 to 3.5 parts by mass of sulfur and 36 to 60 parts by mass of filler for reinforcement comprising not less than 7 parts by mass of silica based on 100 parts by mass of a rubber component comprising : (a) not less than 0% by mass and not more than 20% by mass of (a1) a polybutadiene rubber comprising 2.5 to 20% by mass of 1, 2-syndiotactic polybutadiene crystal and/or (a2) a butadiene rubber synthesized with a rare earth containing catalyst; (b) more than 5% by mass and not more than 60% by mass of (b1) a predetermined tin-modified polybutadiene rubber and/or (b2) a modified butadiene rubber modified with a predetermined compound; and (c) 40 to 75% by mass of a diene rubber other than (a) and (b).