The present invention provides a diene rubber composition having excellent processability
and being improved in both the balance between low rolling resistance and wet skid
resistance, and strength properties. The composition according to the invention
is a diene polymer rubber composition comprising (A) 100 parts by weight of a raw
material rubber comprising (A-1) a diene rubbery polymer which is a conjugated
diene rubbery polymer or a conjugated diene-styrene rubbery copolymer (1) containing
a modified component in an amount exceeding 60 wt. %, which modified component
is obtained by reacting an active end of the rubbery polymer with a polyfunctional
compound having, in its molecule thereof, at least two epoxy groups, (2) having
a molecular weight distribution Mw/Mn of 1.05 to 3.0, and (3) having a weight-average
molecular weight of 100,000 to 2,000,000; and, based on 100 parts of the component
(A), (B) 1 to 100 parts by weight of a rubber extension oil, (C) 25 to 100 parts
by weight of reinforcing silica, and (D) 1.0 to 20 parts by weight in total of
a vulcanizing agent and a vulcanizing accelerator.
