Pneumatic radial tires with rubber filler composed of three rubber stocks

A pneumatic radial tire comprising;

• a tread portion, a pair of sidewall portions extending from both ends of the tread portion, a pair of bead portions extending from the sidewall portions, a carcass extending between a pair of bead cores embedded in the bead portions to reinforce these portions and comprised of at least one rubberized ply containing cords arranged in a radial direction, in which the carcass consists of a main carcass body and a turnup portion wound around the bead core in each bead portion from inside toward outside, a belt superimposed about a crown portion of the carcass to reinforce the tread portion, and a rubber filler taperingly extending from the bead core in each bead portion between the main carcass body and the turnup portion along an outer surface of the main carcass body toward an end of the tread portion, wherein the rubber filler is composed of three rubber stocks having different JIS hardnesses, and a hardest rubber stock having a maximum hardness among these rubber stocks is arranged in at least an outer zone of both zones in the radial direction of the tire sandwiching a normal in drawn from the turnup end to the outer surface of the main carcass body at a cross section of the tire and perpendicular to the main carcass body, and a rubber stock having a hardness between maximum hardness and minimum hardness among these rubber stocks is arranged between the outer surface of the main carcass body and the hardest rubber stock as a stress-mitigating rubber layer, and a softest rubber stock having a minimum hardness among these rubber stocks is arranged along an inner surface of the turnup portion, and the hardness of the stress-mitigating rubber layer is equal to or lower than that of a coating rubber for the cords of the carcass.