| 摘要 |
PURPOSE: To provide a pneumatic radial tire in which a stranding structure is stabilized, and the steering stability and the durability of belt edges are improved in adopting the specified stranding structure as a steel cord of a belt layer. CONSTITUTION: In a pneumatic radial tire, belt layers 6 composed of steel cords whose sections are flat are arranged on the outer periphery of a tread part of a carcass layer 4 so that the major axial direction of the steel cord may extend along the surface direction of the belt layer 6. The steel cord is made into a flatly open stranding structure of 1×6 composed of filaments each of which has the element wire diameter (d) of 0.20 to 0.40mm, and the maj or axis DL of the steel cord taken out from the tire and the strand pitch P are so made to satisfy 3.67d-0.0<=DL<= 3.67d+0.16, and 30d<=P<=45d, and the extension of the steel cord to be generated when the load is increased from 0.25kg to 5.0kg is made to 0.25% or less.
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