A radius of curvature (R1) of a corner portion (40) on one side (an inside in an axial direction) of a groove of a tyre (20) is smaller than a radius of curvature (R2) of the other corner portion (41). Both of the radii of curvature (R1) and (R2) are set to be 2 mm or more. A first phantom circle (42) for defining the corner portion (40) is inscribed on a second phantom circle (43) for defining the corner portion (41). A point of contact (44) of the first phantom circle (42) and the second phantom circle (43) is positioned on an outside from the center of a groove (28c). A distance between the center of the groove (28c) and the point of contact (44) is equal to or smaller than one fifth of a width (B) of the groove (28c).