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 ). <EOS>