Pneumatic tire

A pneumatic tire provided with a tread portion with at least one main groove extending continuously in the tire circumferential direction, wherein

• the main groove, in a cross-section perpendicular to a groove center line, comprises
• a first groove wall consisting of a first portion and a second portion both extending radially inward from a tread surface, said first portion inclined at an angle α1 with respect to a normal line of the tread surface and said second portion inclined at a larger angle α2 than the first portion gradually increasing in an arc-like fashion toward the groove center line,
• a second groove wall consisting of a first portion and a second portion both extending radially inward from the other of the tread surfaces, said first portion inclined at an angle and second portion inclined at a larger angle than the first portion gradually increasing in an arc-like fashion toward the groove center line,
• wherein the incline angles of the first portion and second portion of the first groove wall and second groove wall are such that a width of the main groove is at a maximum at the tread surface and a minimum at a groove bottom, and
• the groove bottom connecting a radially inner end of the first groove wall and a radially inner end of the second groove wall and including a protrusion portion convexed toward the radially outside;
• the protrusion portion continues along the main groove, and, in the axial direction of the tire, the width of the top portion of the protrusion portion is in a range of from 50% to 100% of the maximum groove width of the main groove;
• and
• a cross-sectional area of the protrusion portion outwardly protruding in the tire radial direction from a virtual groove bottom connecting the inner end of the first groove wall and the inner end of the second groove wall with a straight line is in a range of from 3% to 15% of a groove cross-sectional area of the main groove,
• wherein the pneumatic tire is provided in the protrusion portion with a first sipe extending along the groove center line of the main groove;
• wherein a depth of the first sipe is in a range of from 50% to 100% of a radial height from the virtual groove bottom of the protrusion portion at the position provided with the first sipe.