Tire rubber composition and heavy-load tire

The present invention provides: a rubber composition for a tire that achieves both good fuel economy and abrasion resistance, and also achieves good degradation resistance and processability; and a heavy-load tire having a tread produced therefrom. The present invention relates to a rubber composition for a tire, comprising a rubber component that contains a modified natural rubber having a phosphorus content of 200 ppm or less and a butadiene rubber, wherein the amount of the modified natural rubber is 60 to 95% by mass and the amount of the butadiene rubber is 5 to 40% by mass, based on 100% by mass of the rubber component.