Bridgestone Tire Company Limited

Bridgestone Corporation

Nobumasa Ikeda

Takashi Takusagawa

Akio Sato

Hiroshi Hirakawa

Hiroshi Hayakawa

Tamio Araki

Minoru Togashi

Koichi Kojima

Kazuaki Yuto

Yutaka Yamaguchi

Toshio Kita

Toru Oniki

Noboru Kusakabe

Seiichiro Tokunaga

Itsuo Miyake

Nobuyuki Koizumi

Yoshiharu Goto

Masanori Tajima

A paraffin wax composition comprises straight-chain saturated hydrocarbons, wherein the content of each of the straight-chain hydrocarbons having the number of carbons being 22 to 44, respectively, is not less than 2% by weight relative to the entire straight-chain saturated hydrocarbons. A rubber composition is also disclosed, which comprises a rubber and this paraffin wax composition, wherein 1 to 10 parts by weight of the above paraffin wax composition is blended relative to 100 parts by weight of a diene rubber.

Paraffin wax compositions and rubber compositions into which paraffin

Disclosed herein is a pneumatic tire having a tread pattern formed in a tread portion divided into separate blocks at an outer surface of a tread rubber layer in at least a central region of said tread portion by a plurality of main grooves extending circumferentially and a great number of lateral grooves each extending toward a cross direction to each of said main grooves and having a shallower portion as compared with said main groove. The tread portion is a cap-base composite tread portion composed of an upper rubber layer forming a pattern of blocks and a lower rubber layer bordered on said upper rubber layer just therebeneath by a face connecting groove bottoms of said shallower portions of lateral grooves and forming a pattern of ribs separated from one another by said main grooves in the lateral direction and extending substantially continuously in the circumferential direction, and said upper rubber layer is substantially composed of a cap rubber having a JIS hardness at -20.degree. C. of not more than 75.degree. and said lower rubber layer is substantially composed of a base rubber having a JIS hardness at 100.degree. C. of not less than 54.degree. and a loss tangent of not more than 0.22 at 50 Hz, 25.degree. C. and a strain of 2%.

Pneumatic tire tread

A pneumatic radial tire for passenger cars having a low rolling resistance and an excellent wet skid resistance is disclosed. The radial tire comprises a carcass of a radial construction toroidally extending between a pair of bead cores with the ends turned thereover, a tread portion arranged outside a crown portion of the carcass and having a two laminate structure of tread base rubber and tread cap rubber, and a reinforcing belt layer embedded in the tread base rubber and superimposed about the crown portion of the carcass. The tread base rubber and tread cap rubber have resiliences of not less than 65% and not more than 60%, respectively. The tread portion has a sectional ratio of a sectional area of the tread cap rubber occupied in the equatorial section of tire to a total sectional area of the tread portion of not less than 50% and a negative ratio of not more than 45%. The belt layer has a flatness of not more than 15%.

Pneumatic radial tires for passenger cars having low rolling resistance

A pneumatic radial tire is disclosed, which comprises as a reinforcement a belt consisting of a first belt body composed of a single ply containing metal twisted cords arranged at an inclination angle of 5.degree.-25.degree. with respect to the equatorial plane of the tire and embedded in a coating rubber, both end portions in widthwise direction of which being folded on the remaining central base portion thereof, and a second belt body composed of at least one rubberized ply containing inextensible cords crossed with the cords in the base portion of the first belt body. In the first belt body, the coating rubber has a dynamic modulus of 160-400 kg/cm.sup.2 and a gauge of rubber interposed between the cords in the base portion and the cords in the folded portion is within a range of 1.3-4.5 times an average diameter of the cords and is not less than 2 times a gauge of the coating rubber located outside the cords in the base portion opposite to the folded portion.

Pneumatic radial tires

A pneumatic tire having remarkably low rolling resistance and high wet skid resistance without deteriorating the wear resistance is obtained by using in at least the ground-contact area of its tread, a rubber composition consisting essentially of 100 parts by weight of a mixed elastomer and 40-80 parts by weight of carbon black, the mixed elastomer consisting of 10-60 parts by weight of a solution-polymerized styrene-butadiene copolymer rubber having a bonded styrene content of 5-30% by weight and a trans-1,4 content in butadiene unit of not more than 45% by weight; 10-50 parts by weight of an emulsion-polymerized styrene-butadiene copolymer rubber having a bonded styrene content of 30-50% by weight; and 0-80 parts by weight of at least one rubber having a glass transition temperature of not higher than -50.degree. C., which is selected from the group consisting of natural rubber, synthetic polyisoprene rubber, polybutadiene rubber and an emulsion polymerized styrene-butadiene copolymer rubber having a bonded styrene content of 18-28% by weight. The use of carbon black having a specific surface area of 85-95 m.sup.2 /g, a dibutyl phthalate absorption value of 100-110 ml/100 g, a tinting strength of 95-105 and a half value width of at least 180 m.mu. in the size distribution curve of the aggregates is particularly effective for lowering the rolling resistance.

Pneumatic tire

A pneumatic radial tire having a reduced rolling resistance and particularly suitable for a passenger car, comprising a toroidal carcass, a belt layer, a bead core, a side rubber, a tread rubber, a relatively thin base rubber, and a rubber filler, wherein provision is made of a stress relieving groove composed of a depression facing toward the bead rubber at a position near the joint portion between the side rubber and the tread rubber, the base rubber having a resilience which is higher than those of the tread rubber and the bead rubber.

Pneumatic radial tire having a reduced rolling resistance

A pneumatic radial tire for passenger cars having a low rolling resistance is disclosed. The radial tire comprises a body reinforcement including a toroidal carcass composed of radially arranged cords and a belt superimposed about the carcass and consisting of plural rubberized plies each containing cords arranged at 60.degree.-80.degree. with respect to the radial plane of the tire, which cords of said plies being crossed with each other, and a bead reinforcement wherein the carcass is wound around a bead core to form a turnup portion, thread and sidewall rubbers covering these reinforcements. In the radial tire, a super-hard bead filler rubber is arranged at a region extending from the bead core to the middle part of the side portion, and a base rubber having a low loss modulus and a high resilience is arranged on at least both side edge parts of the belt at a volume ratio in the coating rubber for tread portion of 0.1-0.5.

Pneumatic radial tires for passenger cars having a low rolling resistance

A rubber composition containing polyisoprene rubber or a blend of polyisoprene rubber and polybutadiene rubber has a high friction coefficient against the frozen road surface due to the easy deformability at low temperature and high affinity for water. A pneumatic tire comprising a tread consisting of the rubber composition is excellent in the brake, traction and cornering performances and can travel safely on frozen roads without the use of spikes or a chain.

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Kodaira, Japan

Nobumasa Ikeda