Rubber composition for tyres, and pneumatic tyre

A rubber composition for tires, comprising:

• a modified diene rubber containing a functional group reactive with silica;
• a fine particle silica having a nitrogen adsorption specific surface area of 180 m2/g or more and a cetyltrimethylammonium bromide specific surface area of 180 m2/g or more;
• and
• a silane coupling agent represented by the following formula (1):
• [Y1R1Sx—]m[G1(R2SiX1X2X3)a]n[G2]o[R3Y2]p (1)
• wherein each G1 independently represents a C1-C30 polyvalent hydrocarbon group containing a polysulfide group, represented by [(CH2)b—]cR4[—(CH2)dSx—]e;
• each G2 independently represents a C1-C30 polyvalent hydrocarbon group containing a polysulfide group, represented by [(CH2)b—]cR5[—(CH2)dSx—]e;
• each of Y1 and Y2 independently represents a silyl group represented by —SiX1X2X3, a hydrogen atom, a carboxyl group, or an ester group represented by —C(═O)OR6;
• each X1 independently represents —Cl, —Br, —OH, —OR6, or R6C(═O)O—;
• each of X2 and X3 independently represents a hydrogen atom, R6, X1, or a —OSi— containing group formed by silanol condensation;
• each of R1 and R3 independently represents a C1-C20 divalent hydrocarbon group;
• each R2 independently represents a linear hydrocarbon group represented by —(CH2)f—;
• each R4 independently represents a C1-C28 polyvalent hydrocarbon group or a heteroatom-containing C1-C27 polyvalent hydrocarbon group;
• each R5 independently represents a C1-C28 polyvalent hydrocarbon group;
• R6 represents a C1-C20 monovalent hydrocarbon group;
• and
• a, b, c, d, e, f, m, n, o, p, and x are independent from one another, each of a, c, and e represents a number of 1 to 3, each of b and d represents a number of 1 to 5, f represents a number of 0 to 5, each of m and p represents a number of 1 to 100, n represents a number of 1 to 15, o represents a number of 0 to 10, and x represents a number of 1 to 10,
• wherein the modified diene rubber containing a functional group reactive with silica contains at least two selected from the group consisting of a silyl group, an amino group, an amide group, a hydroxy group, and an epoxy group.