Sumitomo Rubber Industries Limited

Akira Manno

Hideaki Yoshikawa

Yukihide Ohya

Yukihide Oya

Yukihide Ouya

A tirehas a beltand a hard rubber layer. The belthas a first ply, a second ply, a third plyand a fourth ply. A width Wof the third plyis smaller than a width Wof the first plyand a width Wof the second ply, and 75% of a width of a tread. Each of the plieshas a steel cord. The first plyand the second plyconstruct a cross-ply structure. A cord of the third plyis wound spirally. The third plyhas what is referred to as a jointless structure. The hard rubber layeris positioned between the first plyand the second ply, and outward of the third plyin an axial direction. A complex elastic modulus of the hard rubber layeris equal to or greater than 30 MPa.

Heavy duty pneumatic tire with belt hard rubber layer

A belt layerof a heavy load radial tire includes second and third belt pliesB andC in which belt cords are arranged at an angle in a range of 10 to 45&#xb0; with respect to a circumferential direction of the tire, and a fourth belt plyD which is disposed outside of the second and third belt pliesB andC and which is spirally wound in the circumferential direction of the tire. When ply widths of the belt pliesB toD are defined as Wto Wand a tread ground-contact width is defined as Tw, the following relations are established: 0.85Tw&#x2266;W, 0.85Tw&#x2266;W, (W&#x2212;W)&#x2267;14 mm, W&#x2267;40 mm. A distance K between a tire equator and an outer end of the fourth belt plyD is in a range of 35% to 40% of the tread ground-contact width Tw. A reinforcing rubber layerhaving the maximum thickness Tof not less than 3.0 mm and a complex elastic modulus E* of in a range of 6.0 to 12.0 MPa is disposed between outer ends of the second and third belt pliesB andC.

Heavy load radial tire

A heavy duty radial tire comprises a belt layer having first and third plies of cords arranged at an angle of 10 to 45&#xb0; relative to the tire equator, and a second ply of cords arranged at an angle of at most 5&#xb0; relative to the tire equator, the widths Wand Wof the first and third plies are at least 85% of a ground contact width Tw and the width Wof the second ply is at least 70% of the width Tw and is smaller than the widths Wand W; and a pair of reinforcing rubber layers disposed between the first and third plies so as to extend axially outwardly from the axially outer ends of the second ply comprising an axially inner portion having E*1 of 8.0 to 14.0 MPa, and an axially outer portion having E*2 of 6.0 to 12.0 MPa smaller than E*1.

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Kobe, Japan

Akira Manno