Abstract: A pneumatic radial tire wherein both end portions of at least one layer of a carcass layer are turned up around right and left bead cores from the inside to the outside of the tire, and at least two layers of belt layers formed by arranging reinforcing cords in such a fashion that their inclining directions with respect to a tire circumferential direction cross one another in mutually opposite directions between the layers are disposed on the outer circumferential side of the carcass layer of a tread portion. A carcass strength coefficient K defined by the formula (1) in the specification is 0.15 to 0.35 N/mm·kPa at portions on the tread portion center side of positions P which are away by 10% of a belt width of a belt layer having the second greatest width from both edges thereof towards its inside, and is 0.5 N/mm·kPa at portions from the positions P to the bead portions.

Abstract: A rubber composition having improved properties containing a starting rubber (e.g., diene rubber) and a polysiloxane having the following alkoxysilyl group (I) and/or acyloxysilyl group (II) and having an average degree of polymerization of 3 to 10,000: ≡Si—OR1  (I) ≡Si—OCOR2  (II) wherein, R1 is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 18 carbon atoms or an organic group containing an ether bond and R2 is hydrogen or a hydrocarbon group having 1 to 21 carbon atoms. The polysiloxane is impregnated in an inert powder.

Abstract: A rubber composition having improved properties containing a starting rubber (e.g., diene rubber) and a polysiloxane having the following alkoxysilyl group (I) and/or acyloxysilyl group (II) and having an average degree of polymerization of 3 to 10,000: ≡Si—OR1  (I) ≡Si—OCOR2  (II) wherein, R1 is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 18 carbon atoms or an organic group containing an ether bond and R2 is hydrogen or a hydrocarbon group having 1 to 21 carbon atoms.

Abstract: A rubber composition having improved properties containing a starting rubber (e.g., diene rubber) and a compounding agent consisting of a silane coupling agent and a carbon black, calcium carbonate or stearic acid powder impregnated with a polysiloxane having the following alkoxysilyl group (I) and/or acyloxysilyl group (II) and having an average degree of polymerization of 3 to 10,000:.tbd.Si--OR.sup.1 (I).tbd.Si--OCOR.sup.2 (II)wherein, R.sup.1 is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 18 carbon atoms or an organic group containing an ether bond and R.sup.2 is hydrogen or a hydrocarbon group having 1 to 21 carbon atoms.

Abstract: A pneumatic tire having an air permeation preventive layer comprising a low permeability thermoplastic elastomer composition comprising a thermoplastic elastomer having a thermoplastic resin composition as a continuous phase and a rubber composition as a dispersed phase, in which a barrier resin composition is contained, which low permeability thermoplastic elastomer composition has a phase structure in which the barrier resin composition is dispersed in the form of a flat state in the thermoplastic elastomer, is abundant in flexibility, is superior in gas permeation preventive property, and enables the tire to be reduced in weight.

Abstract: A rubber composition having improved properties containing a starting rubber (e.g., diene rubber) and a compounding agent comprising a mixture of a polysiloxane having the following alkoxysilyl group (I) and having an average degree of polymerization of 3 to 10,000:.tbd.Si--OR.sup.1 (I).tbd.Si--OCOR.sup.2 (II)wherein, R.sup.1 is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 18 carbon atoms or an organic group containing an ether bond and R.sup.2 is hydrogen or a hydrocarbon group having 1 to 21 carbon atoms, and a sulfur containing silane.

Abstract: A rubber composition containing at least one rubber component containing a diene rubber and a rubber reinforcing carbon black having silica deposited on the surface thereof.

Abstract: A pneumatic tire has an air permeation preventive layer comprising a film composed of a polymer composition containing a thermoplastic resin or a blend of a thermoplastic resin and an elastomer having an air permeation coefficient of not more than 25.times.10.sup.-12 cc.multidot.cm/cm.sup.2 .multidot.sec.multidot.

Abstract: A pneumatic tire to be fitted on a wheel wherein a position, in which a disc is connected to a rim, is offset from the cneter of width of the rim toward the outer surface of the wheel, characterized in that a ratio (Ho/Hi) of an attenuation coefficient Ho (=Go.times.tan.delta.o) determined on the basis of an average thickness Go of an outer side wall of the tire on the outer side of the wheel and a loss factor tan.delta.o of the rubber of this side wall to that Hi (=Gi.times.tan.delta.i) determined on the basis of an average thickness Gi of an inner side wall of the tire on the inner side of the wheel and a loss factor tan.delta.i of the rubber of this side wall is set in the range of 1.2-6.5.

Abstract: A pneumatic tire characterized in that an average thickness G.sub.U of the region of each of side walls which extends from a position corresponding to a widest portion of the tire toward a tread and that G.sub.L of the region of the side wall which extends from the same position toward a bead are set different from each other, the average thickness G.sub.U of the tread-side region being set to not less than 2.5 mm with the average thickness G.sub.L of the bead-side region set to less than 2.5 mm and not less than 1.0 mm.

Abstract: In a pneumatic tire which is to be fitted to a wheel of the type in which connecting position of a disc to a rim is offsetted to a wheel outer side from a center of a rim width, and which has a plurality of blocks on a tread thereof, a pneumatic tire wherein a total contact area C.sub.2 of shoulder blocks on the tire outer side disposed on the offset side of the disc and a total contact area C.sub.1 of shoulder blocks on the tire inner side disposed on the opposite side to the offset side of the disc satisfy the relation, C.sub.1 /C.sub.2 =1.2 to 2.0.

Abstract: A pneumatic radial tire to be fitted on a wheel in which a position wherein a disc is joined to a rim is offset from the center of the width of the rim toward the outer surface of said wheel, characterized in that the tire comprises an asymmetric structure in which a belt layer is provided between a tread and a carcass layer, an outer circumferential portion of the belt layer being covered with at least one belt covering layer, the at least one belt covering layer being disposed so that an average position of the center(s) of the width(s) thereof from the equator of the tire is deviated toward the opposite side of the offset side of the disc, a ratio e/w of the deviating distance e to the width w of a ground contacting portion of the tread being set to 0.05-0.13.

Abstract: A pneumatic radial tire for passenger cars having a plurality of grooves formed in the tread and extending at least circumferentially of the tire, the tread being provided with two belt plies therein. The grooves have a depth in the range of 6.0 to 8.5 mm, with the thickness of the under-groove rubber layer from the bottom of the grooves to the outer belt ply being fixed within the range of 0.5 to 2.5 mm. The belt plies are both made from aramid fiber cords, or either belt ply is made from aramid fiber cords and the other ply from steel cords. The both edge portions of at least one of the belt plies are folded back toward the center of the tread at a fold percentage of 8 to 100 percent.

Abstract: A pneumatic radial tire characterized in that at least two belt layers reinforced with cords of a high elastic modulus extending at an angle of 14.degree.-33.degree. with respect to the circumferential direction of the tire are arranged between a tread and a carcass, at least one of these belt layers being folded back at both end portions thereof toward the equator of the tire so as to wrap both end portions of any remaining belt layers, at least one reinforcing layer which is reinforced with thermally contractible organic fiber cords which extend at substantially 0.degree. with respect to the circumferential direction of the tire being inserted inside of each of the folded portions of the at least one folded belt layer, the width of the reinforcing layers being set to 10-70% of that of each of the folded portions.