A pneumatic tire comprising: a carcass that is disposed toroidally bridging a pair of bead portions, the carcass having a carcass ply that includes plural radial carcass cords and that is equipped with a body portion positioned between the bead portions and with turn-back portions turned back from an inner side to an outer side around bead cores of the bead portions, and the carcass having first sections in which an inter-cord distance between the body portion and the turn-back portions gradually decreases outward in a tire radial direction from the bead cores, second sections that are disposed on the tire radial direction outer sides of the first sections and in which the inter-cord distance between the body portion and the turn-back portions of the carcass ply gradually increases outward in the tire radial direction from the bead cores, and first distance-invariant sections that interconnect tire radial direction outside parts of the first sections and tire radial direction inside parts of the second sections and in which the inter-cord distance between the body portion and the turn-back portions is constant; and stiffeners that are placed between the carcass body portion and the turn-back portions and extend outward in the tire radial direction from the bead cores, characterized in that: a length of the second distance-invariant sections as measured along the tire radial direction is within a range of from 70% to 85% of a rim flange height (Hf) of an applicable rim, wherein the term applicable rim denotes a standard rim of an applicable size described by industrial standards in force in the region where the tire is produced or used: in Japan, JATMA Year Book of the Japan Automobile Tyre Manufacturers Association, Inc.,; in the U.S.A., Year Book of the Tire and Rim Association, Inc.; and in Europe, Standards Manual of the European Tire and Rim Technical Organization. a carcass that is disposed toroidally bridging a pair of bead portions, the carcass having a carcass ply that includes plural radial carcass cords and that is equipped with a body portion positioned between the bead portions and with turn-back portions turned back from an inner side to an outer side around bead cores of the bead portions, and the carcass having first sections in which an inter-cord distance between the body portion and the turn-back portions gradually decreases outward in a tire radial direction from the bead cores, second sections that are disposed on the tire radial direction outer sides of the first sections and in which the inter-cord distance between the body portion and the turn-back portions of the carcass ply gradually increases outward in the tire radial direction from the bead cores, and first distance-invariant sections that interconnect tire radial direction outside parts of the first sections and tire radial direction inside parts of the second sections and in which the inter-cord distance between the body portion and the turn-back portions is constant; and stiffeners that are placed between the carcass body portion and the turn-back portions and extend outward in the tire radial direction from the bead cores, characterized in that: a length of the second distance-invariant sections as measured along the tire radial direction is within a range of from 70% to 85% of a rim flange height (Hf) of an applicable rim, wherein the term applicable rim denotes a standard rim of an applicable size described by industrial standards in force in the region where the tire is produced or used: in Japan, JATMA Year Book of the Japan Automobile Tyre Manufacturers Association, Inc.,; in the U.S.A., Year Book of the Tire and Rim Association, Inc.; and in Europe, Standards Manual of the European Tire and Rim Technical Organization. a length of the second distance-invariant sections as measured along the tire radial direction is within a range of from 70% to 85% of a rim flange height (Hf) of an applicable rim, wherein the term applicable rim denotes a standard rim of an applicable size described by industrial standards in force in the region where the tire is produced or used: in Japan, JATMA Year Book of the Japan Automobile Tyre Manufacturers Association, Inc.,; in the U.S.A., Year Book of the Tire and Rim Association, Inc.; and in Europe, Standards Manual of the European Tire and Rim Technical Organization.