Abstract: An aircraft pneumatic tire that has deeper grooves without causing deterioration in the heat resistance of a top tread and thereby can increase the number of landings per tread is provided. At least part of a top tread 2 in the width direction of the tire has a two-layer structure consisting of a base tread layer 11 and a cap tread layer 12 stacked in the radial outward direction in this order. At least one circumferential groove 4a to 4d is provided in the surface of the top tread 2. The base tread layer 11 and the cap tread layer 12 satisfy the relationships expressed by the following formulas (1) and (2): 1.05<M(50)b/M(50)c?1.30??(1) 1.04<Rb/Rc?1.20??(2) (wherein M(50)b and M(50)c denote 50% moduli of the base tread rubber and the cap tread rubber, respectively, and Rb and Rc denote the resiliences of the base tread rubber and the cap tread rubber, respectively).

Abstract: An aircraft pneumatic tire that has deeper grooves without causing deterioration in the heat resistance of a top tread and thereby can increase the number of landings per tread is provided. At least part of a top tread 2 in the width direction of the tire has a two-layer structure consisting of a base tread layer 11 and a cap tread layer 12 stacked in the radial outward direction in this order. At least one circumferential groove 4a to 4d is provided in the surface of the top tread 2. The base tread layer 11 and the cap tread layer 12 satisfy the relationships expressed by the following formulas (1) and (2): 1.05<M(50)b/M(50)c?1.30 ??(1) 1.04<Rb/Rc?1.20 ??(2) (wherein M(50)b and M(50)c denote 50% moduli of the base tread rubber and the cap tread rubber, respectively, and Rb and Rc denote the resiliences of the base tread rubber and the cap tread rubber, respectively).

Abstract: Steel cord is manufactured by: forming a plurality of bends, per filament length equivalent to one twist pitch, on each of filaments which constitute an outer layer sheath, with the filament length equivalent to one twist pitch being a cycle; twisting these filaments while the bends belonging to the same phase are aligned in a cord axial direction; and subjecting cord side surfaces to compression processing. As a result, flat side surface portions are formed, in which a plurality of filaments forming the outer layer sheath are positioned substantially in the same plane. The steel cord thus formed is used in reinforcement plies for pneumatic radial tires such that the reinforcement plies are laminated in a manner in which the flat side surface portions are mutually parallel.

Abstract: A steel cord comprises a core of three or more filaments bundled without twisting and a sheath of at least one layer comprised of plural filaments wound around the core, wherein all core filaments are arranged in a given rectangle at any section in its longitudinal direction. Such steel cords are used in a belt of a pneumatic tire. And also, these cords are produced by a tubular-type twisting machine having a specified structure.

Abstract: A steel cord for the reinforcement of rubber articles exhibits largely different bending rigidities in two crossing directions at section of the cord and comprises a bundle of plural strands each being obtained by twisting 3 or more steel filaments and a wrapping filament helically wound around the bundle. The steel filaments have a twisting pitch in the range of 3.0 to 30.0 mm. A single wrapping filament is helically wound around the bundle at a twisting pitch of 2.0-15 mm. Various cord structures may be used, for example, 1.times.3, 1.times.5, 2+6 and 3.times.4.

Abstract: A steel cord for the reinforcement of rubber articles exhibits largely different bending rigidities in two crossing directions at section of the cord and comprises a bundle of plural strands each being obtained by twisting 3 or more steel filaments and a wrapping filament helically wound around the bundle.