A passenger tire having a tread, a casing with two sidewalls, one or more radial plies extending from and wrapped about two annular beads and a belt reinforcement structure located radially between the tread and the piles. The tread has a central rib with a first contour-defining curve extending outwards from the mid centerline of the tire towards the sidewalls and a pair of side ribs each having a second contour-defining curve disposed between the central rib and the sidewalls. The first and second contour-defining curves each have first and second radii disposed such that the meeting point of first and second adjacent contour-defining curves cannot contain a single line that is mutually tangential to the first and second adjacent contour-defining curves. First and second circumferential decoupling grooves are disposed on either side of the centerline at the meeting point of the first and second adjacent contour-defining curves, and define a circumferential line at the bottom of the grooves which is a region of greater flexibility than the adjacent ribs of the tire tread to decouple a sidewall bending stresses from the central rib.