To reduce an amount of using 1×N flat open structure steel cords and reduce weight without damaging driving stability and low rolling resistance by a method wherein 1×N' structure steel cords or organic fiber cords are used in addition to the 1×N flat open structure steel cords.
In a pneumatic radial tire having a belt layer 6 formed at a tread part, the belt layer 6 is formed by using steel cords 10 being 1×N flat open structure (N=4-6) wherein N strands 11 with a strand diameter of 0.30-0.38 mm are twisted together and steel cords (or organic fiber cords with a size of 550-6000 denier) 20 being of 1×N' structure (N'=1-3) wherein N' strands with a strand diameter of 0.15-0.5 mm are twisted together. In this case, the steel cords 10 of 1×N flat open structure is formed approximately in an oval shape in cross section and formed such that a flat ratio b/a representing a ratio of a long diameter (b) and a short diameter (a) is 1.6-3.5.
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IGARASHI EIJI
NAKAKITA KAZUMASA
Next Patent: PNEUMATIC TYRE AND MANUFACTURE THEREOF