Wheel rim comprising two rim seats having different diameters, inclined outwards and extended axially outwards by two humps of small height, the rim seat of smaller diameter being connected axially on the inside to a bearing surface via a truncated conical portion and the rim seat of larger diameter being connected axially on the inside to the said bearing surface by a rib of small or zero height, whose axially interior wall has a generatrix that makes with the rotation axis an angle open radially and axially outwards and at the most equal to 30null, characterised in that the said rib, which has an axially inside wall of axial width at most equal to the axial width of the said second seat is provided circumferentially with at least two transverse grooves of small size.