The present invention aims to provide a pneumatic tire with sufficiently reduced rolling resistance. The pneumatic tire according to the present invention including a carcass having a carcass main portion extending from a tread portion via a sidewall portion to a bead portion in a toroidal shape and locked on a bead core embedded in the bead portion, and a belt disposed on a crown portion outer peripheral side of the carcass, characterized in that, when mounted on an applicable rim and put under a predetermined internal pressure no-load condition, a minimum value R1 of a curvature radius of a tire width direction cross-section in a tire radial direction outer portion of the carcass main portion positioned on an tire radial direction outer side than a position where a distance measured from a tire radial direction inner end of the carcass outwardly in the tire radial direction becomes ½ of a carcass cross-sectional height is 0.6 times or less of a minimum value R2 of the curvature radius of the tire width direction cross-section of a portion that, in the tire radial direction inner portion of the carcass main portion positioned on the tire radial direction inner side than the tire radial direction outer portion, bulges out in the tire width direction.

The present invention aims to provide a pneumatic tire with sufficiently reduced rolling resistance. The pneumatic tire according to the present invention including a carcass having a carcass main portion extending from a tread portion via a sidewall portion to a bead portion in a toroidal shape and locked on a bead core embedded in the bead portion, and a belt disposed on a crown portion outer peripheral side of the carcass, characterized in that, when mounted on an applicable rim and put under a predetermined internal pressure no-load condition, a minimum value R1 of a curvature radius of a tire width direction cross-section in a tire radial direction outer portion of the carcass main portion positioned on an tire radial direction outer side than a position where a distance measured from a tire radial direction inner end of the carcass outwardly in the tire radial direction becomes ½ of a carcass cross-sectional height is 0.6 times or less of a minimum value R2 of the curvature radius of the tire width direction cross-section of a portion that, in the tire radial direction inner portion of the carcass main portion positioned on the tire radial direction inner side than the tire radial direction outer portion, bulges out in the tire width direction.

To improve durability performance and rolling resistance performance in a well-balanced manner. It is a tire for heavy loads including a carcass ply (6A). A sidewall rubber (3G) includes an inside rubber part (15) on the carcass (6) side, and an outside rubber part (16) disposed on the outside thereof and forming a tire outer surface. The inside rubber part (15) has a loss tangent tan δ1 less than the outside rubber part (16), and their difference is 0.010 to 0.035. The inside rubber part (15) has a complex elastic modulus less than the outside rubber part (16), their difference is 0.5 to 1.4 (MPa). The outer end (15s) in the tire radial direction of the inside rubber part (15) contacts with the outer surface (2h) in the tire axial direction of the tread rubber (2G), and the inner end (15u) in the tire radial direction is disposed radially inside the outer end (6e) in the tire radial direction of the turned up portion (6b) of the carcass ply (6A).

To improve durability performance and rolling resistance performance in a well-balanced manner. It is a tire for heavy loads including a carcass ply (6A). A sidewall rubber (3G) includes an inside rubber part (15) on the carcass (6) side, and an outside rubber part (16) disposed on the outside thereof and forming a tire outer surface. The inside rubber part (15) has a loss tangent tan δ1 less than the outside rubber part (16), and their difference is 0.010 to 0.035. The inside rubber part (15) has a complex elastic modulus less than the outside rubber part (16), their difference is 0.5 to 1.4 (MPa). The outer end (15s) in the tire radial direction of the inside rubber part (15) contacts with the outer surface (2h) in the tire axial direction of the tread rubber (2G), and the inner end (15u) in the tire radial direction is disposed radially inside the outer end (6e) in the tire radial direction of the turned up portion (6b) of the carcass ply (6A).

This invention is based upon the discovery that micronized solution styrene-butadiene rubber from postconsumer sources can be included in rubber formulations without severely compromising abrasion resistance. The micronized solution styrene-butadiene rubber utilized in the rubber formulations of this invention can be made by cryogenic grinding postconsumer rubber products using conventional procedures. For instance, it can be made by cryogenically grinding a tire tread containing a high level of solution styrene-butadiene rubber. The micronized solution styrene-butadiene rubber can then be blending into desired virgin rubbers and cured without significantly compromising the abrasion resistance of the rubber formulation. The rubber formulation of this invention is comprised of a natural or synthetic rubber and from 1 weight percent to 30 weight percent of a micronized rubber composition containing at least 10 weight percent solution styrene-butadiene rubber and having a particle size of 40 mesh to 200 mesh.

This invention is based upon the discovery that micronized solution styrene-butadiene rubber from postconsumer sources can be included in rubber formulations without severely compromising abrasion resistance. The micronized solution styrene-butadiene rubber utilized in the rubber formulations of this invention can be made by cryogenic grinding postconsumer rubber products using conventional procedures. For instance, it can be made by cryogenically grinding a tire tread containing a high level of solution styrene-butadiene rubber. The micronized solution styrene-butadiene rubber can then be blending into desired virgin rubbers and cured without significantly compromising the abrasion resistance of the rubber formulation. The rubber formulation of this invention is comprised of a natural or synthetic rubber and from 1 weight percent to 30 weight percent of a micronized rubber composition containing at least 10 weight percent solution styrene-butadiene rubber and having a particle size of 40 mesh to 200 mesh.

A low compaction cantilevered tire construction is provided which is designed for use at relatively low inflation pressures and which has sidewalls with a relatively uniform bending resistance through the majority of the sidewall. When the tire is placed under high loads at low inflation pressures the sidewall deflects substantially radially and allows the tread portion of the tire to maintain its intended shape thus improving the contact area of the tire and providing a tire having a relatively high contact area and thus relatively low soil compaction for a given loading.

A low compaction cantilevered tire construction is provided which is designed for use at relatively low inflation pressures and which has sidewalls with a relatively uniform bending resistance through the majority of the sidewall. When the tire is placed under high loads at low inflation pressures the sidewall deflects substantially radially and allows the tread portion of the tire to maintain its intended shape thus improving the contact area of the tire and providing a tire having a relatively high contact area and thus relatively low soil compaction for a given loading.

A tire having uniform inflation growth is provided. The tire includes a body ply that is displaced from the conventional equilibrium curve along the bead, sidewall, and shoulder portions of the tire in a manner that provides more uniform inflation growth from bead portion to bead portion. Such construction reduces load sensitivity, reduces or eliminates the tire break-in period, and/or decreases the propensity for cracking—particularly along a groove bottom of the tread in the shoulder.

A pneumatic tire includes: paired bead portions respectively including annular bead cores and bead fillers disposed on an outer side in a tire radial direction of the bead cores; sidewall portions respectively extending outward in the tire radial direction from the bead portions; a tread portion connected to cuter ends in the tire radial direction of the sidewall portions to form a tread; and a carcass layer suspended between the bead portions. The carcass layer has a first ply that continuously extends between the bead portions and that has opposite end portions respectively and a second ply that continuously extends on the outer side in the tire radial direction of the first ply, wherein the first ply has higher tensile strength than that of the second ply, and the end portion is positioned on the outer side in the tire radial direction of the end.