Pneumatic radial tire

A pneumatic radial tire having a bead portion in which a carcass layer is folded back and turned up around a bead bundle from inside to outside of the tire, at least two reinforcing layers comprising a steel cord reinforcing layer and a fiber cord reinforcing layer are arranged outer to a turnup portion of the carcass layer and, while the steel cord reinforcing layer immediately adjacent the turnup portion of the carcass layer has its upper end located lower to the upper end of the turnup portion, the fiber cord reinforcing layer has its upper end located higher to the upper end of the turnup portion and the upper end of the steel cord reinforcing layer adjacent the turnup portion;

• wherein (1) a rubber stock is disposed between an upper end portion of each of said turnup portion and said fiber cord reinforcing layer to contact and cover the upper end surface of said steel cord reinforcing layer and extend beyond the upper end portion of said fiber cord reinforcing layer, the rubber stock completely covers the upper end portions of the turnup portion and said fiber cord reinforcing layer and axially inner the rubber stock completely covers the side of the fiber cord reinforcing layer;
• (2) that at the location of the upper end of said fiber cord reinforcing layer, the rubber stock has a thickness b in the direction toward the fiber cord reinforcing layer which is 0.5 to 1.5 times the thickness a of the fiber cord reinforcing layer;
• (3) that at the location of the upper end of said turnup portion, the rubber stock has a thickness d between the carcass layer and the fiber cord reinforcing layer which is 1.0 to 4.0 times the cord diameter r of the cords of the steel cord reinforcing layer;
• (4) the upper end of the rubber stock and the upper end of the fiber cord reinforcing layer are spaced from each other by a distance c which is 1.0 to 15.0 times the thickness a of the fiber cord reinforcing layer;
• and (5) that the rubber stock has an elastic modulus which is higher than the elastic modulus of each of the rubber composition in the carcass layer and the rubber composition in the fiber cord reinforcing layer and is also higher than the elastic modulus of each of a bead filler adjacent to the inner side of the rubber stock and a rubber layer adjacent to the outer side of the rubber stock, and the elastic modulus of the rubber stock is within a range of 10 to 15 MPa.