Patent ID: 7874334

Claim:
A pneumatic tire for a motorcycle comprising: a pair of left and right bead cores extending along a circumferential direction of the tire; bead apex rubbers which are respectively disposed at outer sides of the pair of left and right bead cores in a radial direction of the tire and which have triangular cross sections; a carcass which extends between the pair of left and right bead cores in a toroidal shape, which has both ends in a widthwise direction of the tire folded back around the pair of left and right bead cores and retained thereat, and which includes at least one layer of carcass ply having a plurality of rubber-coated carcass cords arranged at an inclination angle of from 60° to 90° with respect to an equatorial plane of the tire; a tread rubber which is provided at an outer side of the carcass in the radial direction of the tire and which constitutes a tread portion; a pair of left and right side rubbers which are provided at the outer side of the carcass in an axial direction of the tire and which constitute a sidewall; and a spiral belt which is provided between the carcass and the tread rubber, which includes at least one belt ply layer formed by spirally winding a rubber-coated cord along the circumferential direction of the tire, and when a region from an edge of a center area that occupies 40% of the tread centered on the tire equatorial plane with respect to the tread surface lateral width, to tread ends is defined as a shoulder area, the spiral belt is disposed to extend across both left and right shoulder areas from the center area of the tread rubber, wherein the number of cords embedded in the spiral belt in the center area is higher than that in the shoulder area, the number of cords embedded in the spiral belt in the center area is set to from 30 to 70/50 mm, the number of cords embedded in the spiral belt in the shoulder area is set to from 10 to 45/50 mm, when the number of cords embedded in the spiral belt in the center area is defined as Nmc and the number of cords embedded in the spiral belt in the shoulder area is defined as Nms, the relationship (A) Nmc/Nms=1.5 to 3.0 is satisfied, when a tangent loss factor of 4% distortion of the tread rubber at 50° C. is defined as tan σ and a dynamic storage elastic modulus is defined as E′, the tread rubber is set to tan σ/E′=0.06 to 0.14 MPa −1 in the center area and the tread rubber is set to tan σ/E′=0.12 to 0.16 MPa −1 in the shoulder area, and when the tan σ/E′ of the tread rubber in the center area is defined as TEc and the tan σ/E′ of the tread rubber in the shoulder area is defined as TEs, the relationship (B) TEc/TEs=0.4 to 0.9 is satisfied.