RUBBER COMPOSITION FOR TIRE

To provide a rubber composition for a tire which is intended mainly for use in a bead filler of a pneumatic tire, has low rolling resistance and has excellent load durability when formed into a tire.SOLUTION: There is provided a rubber composition obtained by blending: 40 to 60 pts.mass of carbon black having a nitrogen adsorption specific surface area NSA of 30 m/g to 70 m/g based on 100 pts.mass of a rubber composition comprising 70 mass% or more of a butadiene rubber containing a syndiotactic 1,2-polybutadiene component and a butadiene rubber containing a terminal-modified butadiene rubber in total; 2.4 to 3.6 pts.mass of sulfur as pure sulfur; and 80 mass% to 110 mass% of a sulfenamide-based vulcanization accelerator based on the sulfur, wherein the molecular weight distribution (Mw/Mn) of the terminal-modified butadiene rubber is set to 2.0 or less, the hardness of the rubber composition is set to 65 to 75 and the tanδ at 60°C is set to 0.05 or less.SELECTED DRAWING: Figure 1 【課題】主に空気入りタイヤのビードフィラーに用いることを意図したタイヤ用ゴム組成物であって、転がり抵抗が低く、且つ、タイヤにした時の荷重耐久性に優れるタイヤ用ゴム組成物を提供する。【解決手段】シンジオタクチック-１，２-ポリブタジエン成分を含有するブタジエンゴムと末端変性ブタジエンゴムとを含むブタジエンゴムを合計で７０質量％以上含むゴム成分１００質量部に対して、窒素吸着比表面積Ｎ2ＳＡが３０ｍ2／ｇ〜７０ｍ2／ｇであるカーボンブラックを４０質量部〜６０質量部、硫黄を純硫黄分で２．４質量部〜３．６質量部、スルフェンアミド系加硫促進剤を前記硫黄に対して８０質量％〜１１０質量％配合し、末端変性ブタジエンゴムの分子量分布（Ｍｗ／Ｍｎ）を２．０以下とし、ゴム組成物の硬度を６５〜７５、６０℃におけるｔａｎδを０．０５以下に設定する。【選択図】図１