An assembly of a wheel rim whose rim diameter is in a range from 12 to 17 inches and a pneumatic tire mounted on the wheel rim, wherein a ratio (SH/SW) of the cross-sectional height SH of the tire to the cross-sectional width SW of the tire is in a range from 0.30 to 0.45, and a ratio (RW/SW) between the width RW of the wheel rim and the cross-sectional width SW of the tire is in a range from 0.78 to 0.99, the pneumatic tire comprising a pair of bead portions each with a bead core embedded therein, a bead apex rubber disposed in one of or alternatively each of the bead portions and extending radially outwardly from a radially outer surface of the bead core so as to have a radially outer end not positioned within a first region, a carcass ply (6A, 6B) extending between the bead portions and turned up around the bead core in each bead portion from the axially inside to the outside so as to form a pair of turned-up portions extending radially outward and a main portion therebetween, and an outside apex rubber disposed axially outward of each of the turned-up portions, wherein the first region is defined between a first tire radial direction line and a second tire radial direction line, when the tire is mounted on a wheel rim, inflated to a specified internal pressure and loaded with no tire load, the specified internal pressure being an air pressure specified for the tire by a standard included in a standardization system on which the tire is based, the first tire radial direction line is a straight line extending in the tire radial direction through a radially outer end of a contact area where the bead portion comes into contact with a flange (Rf) of the wheel rim, and the second tire radial direction line is a straight line extending in the tire radial direction through a position spaced 10 mm axially outward from the radially outer end of the contact area, characterized in that the outside apex rubber is sheet-shaped and has a thickness (d) of not more than 40 % of a maximum axial width (Wa) of the bead apex rubber and the axial distance La between the radially outer end of the bead apex rubber and the radially outer end of the contact area is not more than 2 mm. the pneumatic tire comprising a pair of bead portions each with a bead core embedded therein, a bead apex rubber disposed in one of or alternatively each of the bead portions and extending radially outwardly from a radially outer surface of the bead core so as to have a radially outer end not positioned within a first region, a carcass ply (6A, 6B) extending between the bead portions and turned up around the bead core in each bead portion from the axially inside to the outside so as to form a pair of turned-up portions extending radially outward and a main portion therebetween, and an outside apex rubber disposed axially outward of each of the turned-up portions, wherein the first region is defined between a first tire radial direction line and a second tire radial direction line, when the tire is mounted on a wheel rim, inflated to a specified internal pressure and loaded with no tire load, the specified internal pressure being an air pressure specified for the tire by a standard included in a standardization system on which the tire is based, the first tire radial direction line is a straight line extending in the tire radial direction through a radially outer end of a contact area where the bead portion comes into contact with a flange (Rf) of the wheel rim, and the second tire radial direction line is a straight line extending in the tire radial direction through a position spaced 10 mm axially outward from the radially outer end of the contact area,