A tire comprising: a tread portion comprising a tread edge (Te) and a tire equator, the tread portion being provided with a circumferentially and continuously extending main groove (3, 5) arranged between the tread edge (Te) and the tire equator to define a first land portion between the main groove (3, 5) and the tread edge (Te); the main groove (3, 5) comprising a groove bottom having a deepest depth, an outer groove wall extending radially outwardly and inclined toward the tread edge (Te), and an inner groove wall extending radially outwardly and inclined toward the tire equator; the groove bottom extending in a zigzag manner in a tire circumferential direction in such a manner as to alternate between a first location where the groove bottom is located nearest to the tire equator and a second location where the groove bottom is located nearest to the tread edge (Te); an angle θ2b with respect to a tire normal line of the outer groove wall in a groove cross-section at the second location being greater than an angle θ1a with respect to a tire normal line of the inner groove wall in a groove cross-section at the first location, and characterized in that the main groove (3, 5) comprises a pair of groove edges extending parallel with the tire circumferential direction, and the groove bottom extends oscillating in a tire axial direction with an amplitude of from 0.15 to 0.40 time a groove width of the main groove, wherein the amplitude refers to an axial distance of the oscillating groove bottom between the first location and the second location. a tread portion comprising a tread edge (Te) and a tire equator, the tread portion being provided with a circumferentially and continuously extending main groove (3, 5) arranged between the tread edge (Te) and the tire equator to define a first land portion between the main groove (3, 5) and the tread edge (Te); the main groove (3, 5) comprising a groove bottom having a deepest depth, an outer groove wall extending radially outwardly and inclined toward the tread edge (Te), and an inner groove wall extending radially outwardly and inclined toward the tire equator; a groove bottom having a deepest depth, an outer groove wall extending radially outwardly and inclined toward the tread edge (Te), and an inner groove wall extending radially outwardly and inclined toward the tire equator; the groove bottom extending in a zigzag manner in a tire circumferential direction in such a manner as to alternate between a first location where the groove bottom is located nearest to the tire equator and a second location where the groove bottom is located nearest to the tread edge (Te); an angle θ2b with respect to a tire normal line of the outer groove wall in a groove cross-section at the second location being greater than an angle θ1a with respect to a tire normal line of the inner groove wall in a groove cross-section at the first location, and the main groove (3, 5) comprises a pair of groove edges extending parallel with the tire circumferential direction, and the groove bottom extends oscillating in a tire axial direction with an amplitude of from 0.15 to 0.40 time a groove width of the main groove, wherein the amplitude refers to an axial distance of the oscillating groove bottom between the first location and the second location.