A tire, preferably a radial tire, comprising: a pair of bead cores; a carcass layer having one or more carcass plies extending from one of the bead cores to the other of the bead cores in a toroidal form; and a tread circumferentially encircling the toroidal form of the carcass layer, the tread comprising: a plurality of circumferentially extending tread grooves; one circumferentially extending center rib defined by two of the tread grooves, a radially outer surface of the center rib having a first radius of curvature (TR 1); two circumferentially extending intermediate ribs defined by the tread grooves, a radially outer surface of each intermediate rib having a second radius of curvature (TR 2); and two circumferentially extending shoulder ribs defined by a respective one of said circumferentially extending tread grooves, a radially outer surface of each shoulder rib having a third radius of curvature (TR 3) and a different fourth radius of curvature (TR 4), the third radii (TR 3) each being disposed adjacent one of the respective circumferentially extending tread grooves, the fourth radii (TR 4) each being disposed adjacent an axial outer edge of the tread, the second radii (TR 2) each being greater than the first radius (TR 1) and the third radii (TR 3) being greater than each of the fourth radii (TR 4). a pair of bead cores; a carcass layer having one or more carcass plies extending from one of the bead cores to the other of the bead cores in a toroidal form; and a tread circumferentially encircling the toroidal form of the carcass layer, the tread comprising: a plurality of circumferentially extending tread grooves; one circumferentially extending center rib defined by two of the tread grooves, a radially outer surface of the center rib having a first radius of curvature (TR 1); two circumferentially extending intermediate ribs defined by the tread grooves, a radially outer surface of each intermediate rib having a second radius of curvature (TR 2); and two circumferentially extending shoulder ribs defined by a respective one of said circumferentially extending tread grooves, a radially outer surface of each shoulder rib having a third radius of curvature (TR 3) and a different fourth radius of curvature (TR 4), the third radii (TR 3) each being disposed adjacent one of the respective circumferentially extending tread grooves, the fourth radii (TR 4) each being disposed adjacent an axial outer edge of the tread, the second radii (TR 2) each being greater than the first radius (TR 1) and the third radii (TR 3) being greater than each of the fourth radii (TR 4). a plurality of circumferentially extending tread grooves; one circumferentially extending center rib defined by two of the tread grooves, a radially outer surface of the center rib having a first radius of curvature (TR 1); two circumferentially extending intermediate ribs defined by the tread grooves, a radially outer surface of each intermediate rib having a second radius of curvature (TR 2); and two circumferentially extending shoulder ribs defined by a respective one of said circumferentially extending tread grooves, a radially outer surface of each shoulder rib having a third radius of curvature (TR 3) and a different fourth radius of curvature (TR 4), the third radii (TR 3) each being disposed adjacent one of the respective circumferentially extending tread grooves, the fourth radii (TR 4) each being disposed adjacent an axial outer edge of the tread, the second radii (TR 2) each being greater than the first radius (TR 1) and the third radii (TR 3) being greater than each of the fourth radii (TR 4).