Abstract: A pneumatic tire for a passenger car wherein a plurality of grooves are disposed on a tread surface to define and form land portions, and kerfs which are open to the grooves at at least one of the ends thereof are disposed on the land portions. At least one stage of step portion is disposed in a step shape on at least one of the groove walls of the grooves, and a plurality of kerfs are disposed on the step portion with smaller gaps than those of the kerfs disposed on the land portions.

Abstract: A run-flat pneumatic radial tire having an aspect ratio of up to 50%, which includes a reinforcing liner layer made of a rubber having a complex modulus at 20.degree. C. E*.sub.20, a ratio of a complex modulus at 100.degree. C. to the complex modulus at 20.degree. C., a 100% modulus and a loss tangent (tan .delta.) at 100.degree. C. which satisfy certain specified numeric values. The liner has a crescent sectional shape and is disposed in sidewall portions of a carcass layer with its end portions overlapping the end portions of a belt layer and a bead filler having a specified hardness and height h from a wheel rim base. The carcass layer consists of an inner carcass layer turned up around the bead core from inside to outside the tire so that its end portion is positioned at a position higher than the height h of the bead filler and an outer carcass layer having an end portion disposed axially outward of the bead core.

Abstract: A rubber composition for tire treads is disclosed which is designed to exhibit high resistance to skidding on wet, icy and snowy roads. A selected rubber blend of styrene-butadiene rubber and natural rubber and/or polyisoprene rubber is combined with a selected carbon black of specified specific surface areas and also with a selected softener of specified viscosity-gravity constants. The styrene-butadiene rubber consists essentially of two styrene-butadiene block copolymers each having varied styrene and vinyl contents and a specified transition temperature width, one block having a higher glass transition temperature than the other.

Abstract: A pneumatic tire of a low profile is disclosed which is constructed with a a cap tread, a sidewall and a tie rubber interposed therebetween. The cap tread is formed from a rubber composition comprised of a styrene-butadiene rubber of a high styrene content. The tie rubber comprises a specified sum of a syndiotatic-1,2-butadiene rubber and a cis-1,4-butadiene rubber. Use of the tie rubber is conductive to sufficient adhesion of the tread to the sidewall without shoulder blistering after vulcanization.

Abstract: A radial tire for passenger cars constructed with a sidewall portion formed from a rubber composition having of a volume resistivity of not more than 10.sup.4 .OMEGA.cm. The composition is comprised essentially of a selected rubber and a selected carbon black of an electrically conductive type. The tire is highly resistant to staining with mud and dust while in running and also with dirt pickup during storage.

Abstract: A run flat pneumatic radial tire having a flatness of 50% or less, comprising a reinforcing liner layer comprised of a high-hardness rubber having a crescent cross section disposed on the inside of a side wall portion and an inner liner layer comprising a rubber composition mainly composed of a butyl rubber provided all over the internal surface of the tire, wherein the inside of the inner liner layer in at least a region covering said reinforcing liner layer is covered with a rubber layer comprising a rubber composition mainly composed of a diene rubber having a polybutadiene rubber content of 50% by weight or more based on the rubber component.

Abstract: A run-flat pneumatic radial tire having an aspect ratio of up to 50%, which includes a reinforcing liner layer mode of a rubber having a complex modulus at 20.degree. C. E*.sub.20, a ratio of a complex modulus at 100.degree. C. to the complex modulus at 20.degree. C., a 100% modulus and a loss tangent (tan .delta.) at 100.degree. C. which satisfy certain specified numeric values. The liner has a crescent sectional shape and is disposed in sidewall portions of a carcass layer with its end portions overlapping the end portions of a belt layer and a bead filler having a specified hardness and height h from a wheel rim base. The carcass layer consists of an inner carcass layer turned up around the bead core from inside to outside the tire so that its end portion is positioned at a position higher than the height h of the bead filler and an outer carcass layer having an end portion disposed axially outward of the bead core.

Abstract: A rubber composition for a tire tread comprising a novel modified styrene-butadiene copolymer rubber, carbon black, and aromatic oil.

Abstract: A rubber composition comprising a specific extender oil-extended styrene.butadiene copolymer rubber, at least one other diene rubber and, as required, carbon black, the rubber composition being useful in the preparation of tire treads having decreased rolling resistance without decreasing braking performance. This invention also relates to a specific two-step mixing method for preparing a rubber composition for producing tire treads having further improved rolling resistance and like properties.

Abstract: A pneutmatic radial-ply tire in which the rubber portion of at least one of a carcass ply and an undertread constituting the tire is made of a rubber which has a viscoelastic property of loss tangent, tan.delta., of 0.2 or lower (tan.delta..ltoreq.0.2) and storage modulus, G, of 120 Kg/cm.sup.2 or higher (G.gtoreq.120 kg/cm.sup.2), so that the rolling resistance of the tire is reduced without being accompanied by degradation of braking performance, control stability, comfortableness and wear resistance of the tire.