Patent ID: 7669624

Claim:
A pneumatic tire comprising a tread surface on which a plurality of circumferential groove portions is formed, wherein a first groove portion between a second rib and a shoulder rib is situated closest to a shoulder portion side in a tire width direction among the circumferential groove portions, the first circumferential groove portion includes a first portion and a second portion in a tire circumferential direction, the first portion has a first width at the tread surface, the second portion has a second width at the tread surface, the first width is narrower than the second width, a center of a groove-bottom innermost portion at the first portion is positioned closer to an equatorial surface in the tire width direction than a center of a tread surface groove width at the first portion, the first portion includes an equatorial surface side groove wall and a shoulder portion side groove wall, and a first angle between a virtual extension portion of the tread surface and the equatorial surface side groove wall is equal to or less than a second angle between the virtual extension portion of the tread surface and the shoulder portion side groove wall, the equatorial surface side groove wall includes a first second-rib-side groove wall that is jointed with the tread surface to form the first angle with respect to the virtual extension portion, and a second second-rib-side groove wall that is jointed with the first second-rib-side groove wall to form a corner portion that projects toward the shoulder-portion-side groove wall and forms an angle greater than the first angle with respect to the virtual extension portion, a groove bottom includes a shoulder-rib-side curved surface portion that is projected toward the shoulder rib and jointed with the shoulder portion side groove wall, and a second-rib-side curved surface portion that is projected toward the second rib and jointed with the second second-rib-side groove wall, wherein the shoulder-rib-side curved surface portion has a larger radius of curvature than a radius of curvature of the second-rib-side curved surface portion, and the shoulder-rib-side curved surface portion and the second-rib-side curved surface portion are jointed at the groove-bottom innermost portion.