Patent ID: 8186405
Filing Date: 2012-05-29
Classification: B60C,Y10T

Abstract:
1. A heavy-load radial tire comprising: a carcass comprising a carcass ply, the carcass ply comprising: a ply main portion extending from a tread portion through a side wall portion to a bead core of a bead section; and a ply turnup portion integral with the ply main portion and turned up from an axially inner side of the tire to an axially outer side thereof over the bead core; a bead apex rubber with an approximately triangular cross section radially outwardly extending from the bead core between the ply main portion and the ply turnup portion; and a bead reinforcing cord layer of U-shaped cross section disposed on the bead section and comprising: a base portion disposed on a radially inner side of the bead core; an inner wound-up portion disposed along an axially inner surface of the ply main portion; and an outer wound-up portion disposed along an axially outer surface of the ply turnup portion and terminated at a radially inner side of an radially outermost end of the ply turnup portion, wherein: the bead section is mounted on a 15°-tapered rim; the bead core has a radially outer surface thereof inclined at an angle of 12 to 18° relative to an axial line of the tire, and has an approximately laterally long hexagonal cross section such that a core width Bw oriented in parallel to the radially outer surface of the bead core is larger than a core thickness Bt that is orthogonal to the radially outer surface; the bead apex rubber comprises a lower apex portion of high-elastic rubber disposed on a radially inner side and an upper apex portion of rubber of lower elasticity than that of the rubber of the lower apex portion, the upper apex portion being disposed on a radially outer side; the lower apex portion has an L-shaped cross section composed of a bottom piece portion disposed along the radially outer surface of the bead core and a standing piece portion standing from an axially inner end of the bottom piece portion and radially outwardly extending along the ply main portion, the standing piece portion having a thickness that gradually reduces in a radially outward direction; the upper apex portion of the bead apex rubber has a thickness T the upper apex portion has a thickness T the bead section has a Bw/BL ratio of 0.68 to 0.80, the Bw/BL ratio being a ratio between the core width Bw and an axial bead bottom width BL ranging from a bead heal point to a bead toe end; and the bead section has a W