Pneumatic radial tire

A pneumatic radial tire which has a nominal section width of not less than 255 mm, and an outer diameter of not less than 720 mm, and in which at least one carcass layer is constructed between paired right and left bead cores with the two end portions of the carcass layer being folded back from the inside to the outside of the tire around the respective bead cores in a way that their corresponding bead fillers are enclosed in the two folded end portions of the carcass layer, and in which a belt layer is arranged on the circumference of the carcass layer, wherein:

• the length (Lb) of each bead filler in the radial direction of the tire is 5% to 20% of the section height (SH) of the tire,
• the carcass layer is formed of organic fiber cords made of at least one type of organic fiber which has an expansion ratio of 1% to 5% when a load of 2.0 cN/dtex is applied to the organic fiber,
• a sheet-shaped rubber reinforcement layer with a thickness of 0.5 mm to 2 mm, whose rubber has a larger rubber hardness than that of a sidewall section, is interposed between the carcass layer and the sidewall section on each side of the tire, and
• wherein the length (Lr) of each rubber reinforcement layer in the radial direction of the tire is 40% to 60% of the section height (SH) of the tire,
• wherein said tire includes a base tread and a cap tread and on each side of the tire, the distance, along a carcass line, between the outer end of the rubber reinforcement layer in the radial direction of the tire and an end of said cap tread is in a range of 5 mm to 20 mm.

A pneumatic radial tire which has a nominal section width of not less than 255 mm, and an outer diameter of not less than 720 mm, and in which at least one carcass layer is constructed between paired right and left bead cores with the two end portions of the carcass layer being folded back from the inside to the outside of the tire around the respective bead cores in a way that their corresponding bead fillers are enclosed in the two folded end portions of the carcass layer, and in which a belt layer is arranged on the circumference of the carcass layer, wherein:

• the length (Lb) of each bead filler in the radial direction of the tire is 5% to 20% of the section height (SH) of the tire,
• the carcass layer is formed of organic fiber cords made of at least one type of organic fiber which has an expansion ratio of 1% to 5% when a load of 2.0 cN/dtex is applied to the organic fiber, and
• a sheet-shaped rubber reinforcement layer with a thickness of 0.5 mm to 2 mm, whose rubber has a larger rubber hardness than that of a sidewall section, is interposed between the carcass layer and the sidewall section on each side of the tire,
• wherein on each side of the tire, a fiber reinforcement layer is arranged around the bead core in a way that the fiber reinforcement layer is folded back from the inside to the outside of the tire with the bead filler being enclosed in the folded part of the fiber reinforcement layer, and
• the height (hf) of the outer end in the radial direction of the tire of the fiber reinforcement layer from a bead sheet is 30% to 60% of the section height (SH) of the tire.

A pneumatic radial tire which has a nominal section width of not less than 255 mm, and an outer diameter of not less than 720 mm, and in which at least one carcass layer is constructed between paired right and left bead cores with the two end portions of the carcass layer being folded back from the inside to the outside of the tire around the respective bead cores in a way that their corresponding bead fillers are enclosed in the two folded end portions of the carcass layer, and in which a belt layer is arranged on the circumference of the carcass layer, wherein:

• the length (Lb) of each bead filler in the radial direction of the tire is 5% to 20% of the section height (SH) of the tire,
• the carcass layer is formed of organic fiber cords made of at least one type of organic fiber which has an expansion ratio of 1% to 5% when a load of 2.0 cN/dtex is applied to the organic fiber, and
• a sheet-shaped rubber reinforcement layer with a thickness of 0.5 mm to 2 mm, whose rubber has a larger rubber hardness than that of a sidewall section, is interposed between the carcass layer and the sidewall section on each side of the tire,
• wherein the pneumatic radial tire includes a single carcass layer, and
• on each side of the tire, the end of the folded end portion of the single carcass layer is inserted between the carcass layer itself and the belt layers.