Abstract: A pneumatic tire of the present invention, which has a bead core buried in a bead portion, in which a ratio dw/D of an inner diameter dw of the bead core to a heel diameter D of a rim, which is specified in a public standard, and a ratio dt/D of a heel diameter dt of the bead portion to the heel diameter D of the rim satisfy the following inequalities: 1.009<dw/D<1.022 0.980<dt/D<0.

Abstract: A pneumatic radial tire in which both end portions of a plurality of carcass plies are mounted respectively to left and right bead cores to fold back from an inner side to an outer side of the tire. Fold back portions of the carcass plies constituting the outermost sides on inner sides of the bead cores are laminated onto unfolded portions of the carcass plies. Carcass cords of the carcass plies are intersected with each other between the laminated layers. A length of the fold back portion is longer than any of fold back portions of the remaining carcass plies.

Abstract: A pneumatic tire of the present invention, which has a bead core buried in a bead portion, in which a ratio dw/D of an inner diameter dw of the bead core to a heel diameter D of a rim, which is specified in a public standard, and a ratio dt/D of a heel diameter dt of the bead portion to the heel diameter D of the rim satisfy the following inequalities:

Abstract: A pneumatic radial tire having carcass layers of three plies each constituted by organic fiber cords and in which both end portions of a first one and a second one of the carcass layers enumerated from an inner side to an outer side direction of the tire in the 3 plies of carcass layers, are folded back from the inner side to the outer side of the tire respectively around bead cores, reinforcement layers are arranged on outer sides of the fold back portions of the carcass layers and a third one of the carcass layers is turned down to cover outer sides of the reinforcement layers.

Abstract: A pneumatic tire wherein a plurality of righthand oblique groove groups each group of which has a plurality of righthand oblique grooves as extending obliquely to a reverse tire turning direction from a tread center portion to a righthand shoulder end and a plurality of lefthand oblique groove groups each group of which has a plurality of lefthand oblique grooves extending obliquely to the reverse tire turning direction from the tread center portion to a lefthand shoulder end are disposed alternately in a tire circumferential direction on a tread surface which has a tire turning direction designated in one direction in such a manner that one main rib is defined in a zigzag shape in the tire circumferential direction by starting end portions of the righthand oblique groove groups and by starting end portions of the lefthand oblique groove groups and lefthand and righthand sub ribs are branched from the main rib along the righthand oblique groove groups and the lefthand oblique groove groups, respectively.

Abstract: At least one reinforcing rubber layer is provided in the part of each of two side wall portions which is on the outer side of a carcass layer. The outer circumferential end portions of the reinforcing rubber layers extend to positions in which they are disposed between the end portions of the innermost belt layer and the corresponding portions of the carcass layer, while the inner circumferential end portions of these rubber layers extend inward in the radial direction of the tire so as to overlap the bead fillers in positions on the outer sides of the end portions of the carcass layer in the widthwise direction of the tire. A 100% modulus at 100.degree. C. of the rubber constituting the reinforcing rubber layers is not higher than that of the rubber of the belt layers, and a dynamic elastic modulus at 20.degree. C. of the former rubber in the range of 10-40 MPa.

Abstract: A pneumatic tire wherein an end portion of a carcass layer is turned up from inside to outside of the tire around each bead core up to a buttress portion, and this turn-up end portion is clamped between a belt edge cushion rubber and an under-tread rubber.