Patent ID: 8622105

Claim:
A pneumatic tire comprising a carcass extending between a pair of bead portions through a tread portion and a pair of sidewall portions, and a band made of at least one spirally wound cord disposed radially outside the carcass in the tread portion, wherein the band cord consists of materially identical high-strength high-modulus organic filaments, and the band cord is obtainable by the following process: the high-modulus organic filaments are divided into a plurality of bunches, the bunches are each first twisted separately from each other, the first twisted bunches are each subjected to a dip-and-stretch treatment, and the treated bunches are second twisted together, wherein the first twisted bunches include a low-twist bunch of which first twist number is a minimum value Nmin, and a high-twist bunch of which first twist number is a maximum value Nmax, and the ratio Nmin/Nmax is not less than 0.5 and not more than 0.9, and the second twist number M of the treated bunches is not less than the minimum value Nmin and not more than the maximum value Nmax; whereby the band cord has a load-elongation curve comprising a low-modulus zone between the origin and a boundary point (P) and a high-modulus zone between the boundary point (P) and the breaking point (P 1 ), and the boundary point (P) is at a certain elongation in a range of from 1 to 7%, and the ratio EH/EL of a nominal elastic modulus EH of the high-modulus zone and a nominal elastic modulus EL of the low-modulus zone is in a range of from 2.0 to 10.0, wherein the boundary point (P) is defined as a point on the load-elongation curve (J) of which elongation percentage is the same as that of an intersecting point (P 0 ) between two tangential lines (T 1 and T 2 ) to the load-elongation curve (J) at the origin ( 0 ) thereof and the breaking point (P 1 ) of the cord, the nominal elastic modulus EL of the low-modulus zone (S 1 ) is defined by the slope of a straight line drawn between the origin (O) and the boundary point (P), the nominal elastic modulus EH of the high-modulus zone (S 2 ) is defined by the slope of a straight line drawn between the boundary point (P) and breaking point (P 1 ), the load-elongation curve (J) extends from the boundary point (P) toward the origin (O) asymptotically to the tangential line (T 1 ) between the origin ( 0 ) and the intersecting point (P 0 ), and the load-elongation curve (J) extends from the boundary point (P) toward the breaking point (P 1 ) asymptotically to the tangential line (T 2 ) between the breaking point (P 1 ) and the intersecting point (P 0 ).