| 摘要 |
PROBLEM TO BE SOLVED: To enhance anti-separation property of a belt layer while restricting eccentric wear, etc., thereof by forming a steel cord in a single twist constituting of plural elemental wires, setting the arranged sectional surface in a circular shape, regulating the relationship between an internal between elemental wires and its exclusive occupational rate by means of a certain conditional formula and winding the steel cord at a small angle relatively to a tire peripheral direction. SOLUTION: The reinforcing cord of a belt layer to be arranged outside of mutually adjacent belt layers 6... is composed of a steel cord (s) and also the steel cord (s) is formed in a spiral structure wound at arrangement angle relative to the tire peripheral direction, to less than 5 deg.. The steel cord (s) is composed of a single twist steel cord formed by twisting plural elemental wires f and also those elemental wires (f) are formed in such arrangement as the tire radial sectional areas being aligned in a circular arc at the tread part 3, the entire sum of number of elemental wires (n), elemental wire diameter (d), and a distance between centers of mutually adjacent elemental wires, is defined toΣ1 and the outer diameter of the steel cord is defined to D, equationsΣ1<1.16d (n-1), and 1.6<dn/(D-d)<3.0 are satisfied.
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