A tire has a tread 5 which includes grooves 7, the side faces 72 of which are undercut, and includes at least one circumferential reinforcing element 8-1 arranged axially relative to said undercut side face 72 at a distance “d” of between 0 and 15% of the axial width L51 of the tread block 51, at least extending radially from the inside towards the outside from a radial level situated above the wear limit level and to a radial height equal to 5% of the thickness “p” of the tread.