Heavy duty tire

A heavy duty tire comprising a tread having a tread surface that comes into contact with a road surface, wherein

• in the tire in a normal state where the tire is mounted on a normal rim, an internal pressure of the tire is adjusted to a normal internal pressure, and no load is applied to the tire, a profile of the tread surface includes a crown circular arc as a circular arc representing a profile of a portion including an equator, and the crown circular arc has a radius of not less than 1600 mm and not greater than 2000 mm, and
• when a ratio of an equator ground-contact length measured along the equator, to a reference ground-contact length at a position corresponding to a width that is 70% of a maximum ground-contact width, on a ground-contact surface obtained when a load is applied to the tire in the normal state and the tread surface is brought into contact with a flat road surface, is defined as a shape index, the shape index obtained when the load is 30% of a normal load is defined as an ultra-light load shape index, and the shape index obtained when the load is 60% of the normal load is defined as a light load shape index,
• the ultra-light load shape index is higher than the light load shape index, the ultra-light load shape index is not less than 1.10 and not greater than 1.20, and the light load shape index is not less than 1.04 and not greater than 1.14.