Abstract: A pneumatic radial tire comprises a tread provided with a plurality of circumferential grooves extending in a circumferential direction of the tire, and plural rows of land portions defined between axially adjacent circumferential grooves and between each of edges of the tread and the adjacent main circumferential groove. That groove wall of at least the circumferential groove located nearest to at least one of the tread edges on a treading surface of the tread which is positioned on a side of the one of the tread edges is inclined to gradually increase a width of the groove toward the surface of the tread from a location spaced by 10-70% of a depth of the circumferential groove radially outwardly from a bottom thereof. The width of an opening of the circumferential groove to the surface of the tread is in a range of 3-18 mm.

Abstract: To improve the tire transversal rigidity and further the tire contact area with the ground, that is, to improve the tire cornering power or vehicle turning performance, the tire inner sidewall portion is reinforced by a carcass turned-up end portion, a hard rubber filler, and at least one inclined cord layer by extending all the radially outward ends thereof to roughly the middle of the tire sidewall. Further, the maximum carcass width position is located radially outward away from a bead heel by a distance (V) of at least 60% of a tire section height (J) before inflation but located radially outward away from the bead heel by a distance (U) of about 55 to 75% of the above before-inflation distance (V) after inflation, and the axial bead heel distance (A) between the two opposite beads before inflation is determined smaller than that (B) therebetween after inflation.