Abstract: Each of belt layers of a pneumatic radial tire includes a plurality of single steel wires with an identical wire diameter extending linearly in an identical direction in alignment with each other and embedded in rubber. Each of the wires is provided with axial torsion. On the outer surface of a tread portion, circumferential grooves extend in the circumferential direction of the tire. The wire diameters of the single steel wires are 0.28 mm to 0.38 mm. An average of intervals of the single steel wires is not less than 0.10 mm. The tire has an out-of-plane bending stiffness of not less than 6000 N·mm2 per inch of length of the tread portion in the circumferential direction when a force application point is located at the circumferential groove. The implanted density E (wires/50 mm) of the single steel wires satisfies E?1869×d2?1838×d+493, where d is the wire diameter.

Abstract: Each of belt layers of a pneumatic radial tire includes a plurality of single steel wires with an identical wire diameter extending linearly in an identical direction in alignment with each other and embedded in rubber. Each of the wires is provided with axial torsion. On the outer surface of a tread portion, circumferential grooves extend in the circumferential direction of the tire. The wire diameters of the single steel wires are 0.28 mm to 0.38 mm. An average of intervals of the single steel wires is not less than 0.10 mm. The tire has an out-of-plane bending stiffness of not less than 6000N·mm2 per inch of length of the tread portion in the circumferential direction when a force application point is located at the circumferential groove. The implanted density E (wires/50 mm) of the single steel wires satisfies E?1869×d2?1838×d+493, where d is the wire diameter.

Abstract: This invention relates to a pneumatic tire with an improved driveability and a reduced weight as well as a maintained traveling durability, and particularly a pneumatic tire having a high post cure inflation pressure, and being best suited as a pneumatic tire for a light truck with a high air pressure. In the pneumatic tire, twisted cords formed of a polyketone fiber represented by the following formula (a), and having a thermal shrinkage stress value, at a dry heat temperature of 150° C., of not less than 0.19 cN/dtex are used as cords for forming a carcass layer: —(CH2—CH2—CO)n-(R—CO—)m-??formula (a); where the relationship between n and m is represented by the following formula (b), and R represents an alkylene group having 3 or more carbon atoms: 1.05?(n+m)/n?1.00??formula (b).

Abstract: Disclosed is a pneumatic tire which comprises belt layers in a tread part and belt cover layers formed by winding organic fiber cords spirally and continuously in the tire circumferential direction on outer peripheries of at least both edge portions of the belt layer respectively. The organic fiber cords are twisted cords of at least one polyketone fiber yarns having a heat shrinkage stress at 150° C. of 0.19 to 0.60 cN/dtex.

Abstract: A pneumatic radial tire allowing to improve the high speed endurance and the road noise considerably. The pneumatic radial tire has a carcass layer mounted between a pair of right and left bead portions and a belt layer embedded in the outer peripheral side of the carcass layer in a tread portion, and a belt cover layer comprising fiber cords made of filaments of polyolefin ketone having a structure represented by the following formula (1) is disposed around the outer peripheral side of the belt layer, and an elongation rate of the fiber cords composing the belt cover layer is equal or inferior to 2.5% in the tire; —(CH2—CH2—CO)n—(R—CO)m—  (1) where, 1.05≧(n+m)/n≧1.00, R is an alkylene group having three or more carbons.

Abstract: A pneumatic radial tire allowing to improve the high speed endurance and the road noise considerably. The pneumatic radial tire has a carcass layer mounted between a pair of right and left bead portions and a belt layer embedded in the outer peripheral side of the carcass layer in a tread portion, and a belt cover layer comprising fiber cords made of filaments of polyolefin ketone having a structure represented by the following formula (1) is disposed around the outer peripheral side of the belt layer, and an elongation rate of the fiber cords composing the belt cover layer is equal or inferior to 2.5% in the tire.

Abstract: A pneumatic radial tire includes a belt layer, comprised of steel cords having a lateral flat cross-section, arranged around an outer periphery of a tread portion of a carcass layer so that the diameter direction of the steel cords is made to follow the planar direction of the belt layer, the steel cord is made a flat 1.times.6 twist structure comprised of filaments of a filament diameter d of 0.20 to 0.40 mm, the long diameter D.sub.L and twist pitch P of the steel cord taken out from the tire are made with respect to the filament diameter d as follows:3.67 d-0.04.ltoreq.D.sub.L .ltoreq.3.67 d+0.1630d.ltoreq.P.ltoreq.45dand the elongation of the steel cord caused when increasing a load from 0.25 kg to 5.0 kg is made 0.25% or less.