TIRE RUBBER COMPOSITION

To provide a tire rubber composition which can preferably improve and maintain stability and durability when being used for a tire, and reduce rolling resistance.SOLUTION: There is provided a tire rubber composition including, with respect to 100 pts.mass of a rubber component including 50 mass% or greater of natural rubber and 10 mass% to 40 mass% of butadiene rubber: 35 pts.mass to 60 pts.mass of carbon black whose CTAB adsorption specific surface area is lower than 70 m2/g; and 3 pts.mass to 30 pts.mass of silica whose CTAB adsorption specific surface area is lower than 180 m2/g, and as the butadiene rubber, the butadiene rubber which is not modified is used in which: cis-1,4-coupling percentage content is 97% or greater and Mooney viscosity ML1+4 at 100°C is equal to or greater than 45, and a ratio Tcp/ML1+4 between 5 mass% toluene solution viscosity Tcp (unit is cps) at 25°C and the Mooney viscosity ML1+4 is 2.0 to 3.0.SELECTED DRAWING: Figure 1 【課題】タイヤに使用したときに、操縦安定性や耐久性を良好に維持・改善しながら、転がり抵抗を低減することを可能にしたタイヤ用ゴム組成物を提供する。【解決手段】天然ゴム５０質量％以上とブタジエンゴム１０質量％～４０質量％とを含むゴム成分１００質量部に対して、ＣＴＡＢ吸着比表面積が７０ｍ2／ｇ未満であるカーボンブラック３５質量部～６０質量部と、ＣＴＡＢ吸着比表面積が１８０ｍ2／ｇ未満であるシリカ３質量部～３０質量部とを配合し、ブタジエンゴムとして、シス－１，４結合含有率が９７％以上であり、１００℃におけるムーニー粘度ＭＬ1+4が４５以上であり、２５℃における５質量％トルエン溶液粘度Ｔｃｐ〔単位：ｃｐｓ〕と前記ムーニー粘度ＭＬ1+4との比Ｔｃｐ／ＭＬ1+4が２．０～３．０である未変性のブタジエンゴムを用いる。【選択図】図１