Heavy-duty tire rubber compositions and tires

A heavy-duty tire rubber composition, comprising:

• 100 parts by mass of a solid rubber (A),
• 0.1 to 50 parts by mass of a modified liquid diene rubber (B), the modified liquid diene rubber (B) comprising a functional group derived from a silane compound, and
• 20 to 200 parts by mass of a filler (C),
• wherein the solid rubber (A) comprises 60 mass % or more of a natural rubber, and
• wherein the modified liquid diene rubber (B) satisfies the following conditions (i) and (ii):
• (i) a weight average molecular weight is not less than 1,000 and not more than 120,000, and
• (ii) a vinyl content is not less than 30 mol % and less than 70 mol %, and
• the silane compound is a compound of formula (1):
• wherein R1 is a C1-6 divalent alkylene group, and R2, R3 and R4 are each independently a methoxy group, an ethoxy group, a phenoxy group, a methyl group, an ethyl group or a phenyl group, wherein at least one of R2, R3 and R4 is a methoxy group, an ethoxy group or a phenoxy group.