The Yokohama Rubber Co., Ltd.

Masahiko Kanamaru

Osamu Takahashi

Kazuyuki Kabe

Ken Takahashi

A pneumatic radial tire having a circular bead core of substantially polygonal cross section which includes a base (a) adjacent an inclined bead base portion of the tire, an inner side (b) on a side of the bead core nearest a bead toe portion of the tire, an outer side (d) on a side of the bead core nearest a bead heel portion of the tire, and a top side (c) opposite the base (a) and joining the inner side (b) and the outer side (d). An inclination .theta..sub.1 of the base (a) relative to the axial direction of the tire is substantially the same as that of the bead base portion relative to the axial direction of the tire. A cross angle .beta. between the base (a) and the inner side (b) is 70.degree. to 90.degree.. An inclination .theta..sub.2 of the top side (c) relative to the axial direction of the tire is smaller than the inclination .theta..sub.1 and the direction of inclination of the top side (c) is opposite to that of the base (a).

Pneumatic tire with polygonal bead core

A heavy-duty pneumatic tire having a plurality of belt layers, wherein the outermost belt layer is made of a steel cord having a breaking extension of 4% or more and covers the end portion in the width direction of a first belt layer adjacent to the undersurface of said outermost belt layer, a rubber stock is provided on the outside of the end portion in the width direction of said first belt layer, the cord of said first belt layer and the cord of a second belt layer adjacent to the undersurface of said first belt layer are each inclined at an angle of 15.degree. to 25.degree. with respect to the circumferential direction of the tire and cross each other.

Heavy-duty pneumatic tire preventing belt separation

A heavy loading tubless tire comprising a bead portion which has a buried bead core bundled of a plurality of bead wires and having a polygonal section contour and which has its bead base composed of two regions: a region W.sub.1 located at the side of the bead heel and inclined at an angle substantially equal to the angle .theta. of inclination of a rim base with resepct to the axis of tire rotations; and a region W.sub.2 located at the side of the bead toe and inclined at a larger angle than the angle .theta. of inclination of said rim base, wherein the improvement resides: in that the width of the region W.sub.2 at the side of said bead toe measured in the axial direction of tire rotations is within a range of 30 to 70% of the total width of the bead base measured in the axial direction of tire rotations whereas the width of said bead core measured in the axial direction of tire rotations is at least 40% as large as the total width of said bead base; and in that the bottom side of the polygonal contour of said bead core at the side of the bead base is composed of a bottom side a.sub.1, which is located at the side of the bead heel and inclined at an angle .theta.a substantially equal to the inclination angle .theta. of said rim base, a bottom side a.sub.2, which is located to merge into said bottom side a.sub.1 and inclined at an angle .theta.b larger than the inclination angle .theta. of said rim base, and a bottom side a.sub.3 which is so located at the side of the bead toe as to project from the extension of said bottom side a.sub.1 toward said bead base.

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Zushi, Japan

Masahiko Kanamaru