Pneumatic tire for heavy load

A pneumatic tire for heavy load comprising:

• three circumferential main grooves extending on a tread in the circumferential direction;
• and
• ribs defined by these circumferential main grooves,
• characterized in that the centerline of the center circumferential main groove among the three circumferential main grooves is positioned on the equator line of the tread, and
• that a thin rib-shaped uneven abrasion sacrificing part having a step in a clearance thereof from the surface of the tread is formed only in the center circumferential main groove, and
• that the center circumferential main groove involves see-through groove portion extending to the straight, and
• that, when the step of the thin rib-shaped uneven abrasion sacrificing part formed in the clearance thereof from the surface of the tread is indicated by d, and a depth of the center circumferential main groove is indicated by D, the relationship expressed by the formula 0.7D≦(D−d)≦D−3 mm is satisfied,
• wherein the width of the thin rib-shaped uneven abrasion sacrificing part is in a range of from 2 to 10% of the width of the tread,
• wherein the width of the thin rib-shaped uneven abrasion sacrificing part is narrower than a width of adjoining ribs,
• wherein the position of the deepest groove portion of each of the opposite-side circumferential main grooves changes along the circumferential direction of the tire in the circumferential main groove at a predetermined interval in the width direction of the tread, and
• wherein depth-direction positions at which perpendicular lines perpendicular or approximately perpendicular to the surface of the tread and passing through edges of the ribs at the sides of the circumferential main grooves are in contact with a groove bottom surface of the circumferential main groove, and angles each of which includes the corresponding depth-direction position as a vertex and is formed by the corresponding perpendicular line and a cross-sectional line of the groove bottom surface extending in the width direction of the tread, change along the circumferential direction at a predetermined interval.