Pneumatic tire for two-wheeled motor vehicles

1. A pneumatic tires for two-wheeled motor vehicles in which a tread width comprises a tire maximum width and in which a tread surface warps in an arc-like manner within a tire meridian section, the tire comprising:

a carcass comprised of a single carcass ply including organic fiber cords that extend between a pair of bead portions in a toroidal manner,

a belt layer disposed outside of the carcass in a radial direction and comprised of at least one belt ply formed by spirally winding a tape-like member of small width obtained by coating one or a plurality of steel cords with topping rubber so that the steel cords are substantially parallel to a tire circumferential direction, and

a tread reinforcing layer disposed outside of the belt layer in the tire radial direction and comprised of a single reinforcing ply in which organic fiber cords are aligned to be substantially parallel to the tire circumferential direction,

wherein the reinforcing ply has a width in a tire axial direction of not less than 30 mm and not more than 90% of a tread grounding width.

2. The pneumatic tires for two-wheeled motor vehicles as claimed in claim 1 , wherein the reinforcing ply is formed by winding a ply member of large width obtained by coating a plurality of organic fiber cords with topping rubber and by cutting both ends thereof in the circumferential direction, by a single round in the tire circumferential direction.

3. The pneumatic tires for two-wheeled motor vehicles as claimed in claim 1 , wherein the reinforcing ply is formed by spirally winding a tape-like member of small width obtained by coating one or a plurality of organic fiber cords with topping rubber.

4. The pneumatic tires for two-wheeled motor vehicles as claimed in any one of claims 1 to 3 , wherein the belt layer is comprised of a single belt ply, and wherein its width BW in the tire axial direction is 300 to 370% of the tread grounding width.

5. The pneumatic tires for two-wheeled motor vehicles as claimed in claim 1 , wherein the organic fiber cords of the reinforcing ply are arranged such that a mass fineness D 2 of cord is smaller than a mass fineness D 1 of the organic fiber cord of the carcass ply.

6. The pneumatic tires for two-wheeled motor vehicles as claimed in claim 5 , wherein the organic fiber cords of the carcass ply are comprised of rayon cords and the organic fiber cords of the reinforcing ply are comprised of nylon cords.

7. The pneumatic tires for two-wheeled motor vehicles as claimed in claim 6 , wherein the nylon cords of the reinforcing play have a mass fineness D 2 of not more than 1880 dtex.

8. The pneumatic tires for two-wheeled motor vehicles as claimed in claim 7 , wherein the nylon cords of the reinforcing play have a two folded yarn structure.

9. The pneumatic tires for two-wheeled motor vehicles as claimed in claim 5 , wherein the carcass play is arranged such that a cord implantation number N 1 per 5 cm of ply width is smaller than the cord implantation number N 2 of the reinforcing ply, and wherein a product N 1 ×D 1 of the cord implantation number N 1 and the mass fineness D 1 of cord of the carcass play is larger than a product N 2 ×D 2 of the cord implantation number N 2 and the mass fineness D 2 of cord of the reinforcing ply.

10. The pneumatic tires for two-wheeled motor vehicles as claimed in claim 1 , wherein the reinforcing ply is arranged such that cord implantation number N 2 per 5 cm of ply width is 50 to 80 (cords/5 cm).