Pneumatic radial tires with monostrand bead core for small-size passenger cars

A pneumatic radial tire for a small-size passenger car comprising;

• a tread portion, a pair of sidewall portion extending from both side ends of the tread portion, and a pair of bead portions each including a bead core therein and extending from an inner peripheral end of the sidewall portion, said bead core being a monostrand bead core having a compact unit structure of 3 to 10 steel wire windings in cross-section and formed by spirally winding a steel wire of circular cross-section covered with a coating rubber and binding the steel wire windings into a bundle, said steel wire having a diameter (D) of 1.2-2.2 mm, and a ratio of distance between center points of adjacent steel wire windings in said bead core (H) to the diameter (D) of said steel wire is within a range of 1.01-1.2, and a length L in mm overlapping a winding start point of said steel wire with a winding terminal point thereof satisfies the following equation:
• L.gtoreq.4.0.times.10.times..pi.r.sup.2 .times.(f/A)
• wherein r is a radius in mm of the steel wire, f is a tensile strength in kgf/mm.sup.2 of the steel wire and A is a drawing force in kgf of the steel wire from the coating rubber.