Heavy duty tire

A heavy duty tire having

• a carcass extending from a tread portion to bead cores in bead portions through sidewall portions, and
• a belt layer composed of a plurality of belt plies disposed in the tread portion and on the outside of the carcass in the tire radial direction,
• wherein
• in a state in which a distance between a pair of bead heels of the tire is kept at 110% of a wheel rim width of a standard wheel rim and no inner pressure is applied,
• a contour shape of the tread portion in a tire meridian section consists of a 1st circular arc having a center on the tire equatorial plane, and a pair of 2nd circular arcs located one on each side of the 1st circular arc in the tire axial direction, and
• one of the 2nd circular arcs has a center on the other 2nd circular arc side of the tire equator in the tire axial direction, and the other 2nd circular arc has a center on said one 2nd circular arc side of the tire equator in the tire axial direction,
• the 1st circular arc is connected to the 2nd circular arcs smoothly at connecting points from which the 2nd circular arcs extend to respective tread edges, and
• a ratio R2/R1 of a radius R2 of the 2nd circular arcs to a radius R1 of the 1st circular arc is 1.50 to 2.20,
• in a normal state in which the tire is mounted on the standard wheel rim, inflated to a standard inner pressure and loaded with no tire load,
• a contour shape the tread portion in a tire meridian section consists of a 3rd circular arc having a center on the tire equatorial plane, and a pair of 4th circular arcs located one on each side of the 3rd circular arc in the tire axial direction,
• the 3rd circular arc is connected to the 4th circular arcs smoothly at connecting points from which the 4th circular arcs extend to the respective tread edges, and
• a ratio R4/R3 of a radius R4 of the 4th circular arcs to a radius R3 of the 3rd circular arc is 1.05 to 1.25.