A pneumatic tire comprising an annular tread portion (10) including a plurality of circumferentially extending main grooves (20, 21, 22) comprising an axially innermost groove (22), an axially outermost groove (20), and at least one middle groove (21) arranged between the innermost groove and the outermost groove is disclosed; the outermost groove (20) has an asymmetric cross section with respect to any straight line perpendicular to the groove opening and comprises an inner sidewall (24), an outer sidewall (23), a groove bottom (25) and a groove opening opposite to the groove bottom (25), wherein the outer sidewall (23) is tilted by more than 20°with respect to a straight line perpendicular to the groove opening