To provide a pneumatic radial tire having a nominal tire sectional width of 255 or greater and a tire outer diameter of 720 mm or larger and compatibly attaining control stability and a lighter weight.
At least one carcass layer 6 is mounted between a pair of right and left bead cores 4. Both ends of the carcass layer 6 are turned from the inside of the tire back to the outside so as to hold bead fillers 5 around the bead cores 4. A tire radial length Lb of the bead filler 5 is 5-20% of a tire sectional height SH. The carcass layer 6 is formed with organic fiber cords consisting of at least one type of organic fibers having elongation percentages of 1-5% during applying a load of 2.0 cN/dtex. A sheet rubber reinforcing layer 7 which has a rubber hardness greater than the rubber of a sidewall portion 2 and a thickness of 5-2 mm is laid between the carcass layer 6 and the sidewall portion 2.
Takashi Noguchi
Kazuhiko Saishita