A rim for a tire , comprising: a main tubular body extending around a rotation axis of the rim and having a cylindrical surface extending between two lateral edges and, in use, facing the tire ; a bead-seat having a greater diameter than the cylindrical surface of the tubular body and overlapped to it; said bead-seat comprising an external portion with respect to a space occupied, in use, by the tire and an elongated portion extending inside the space occupied, in use, by the tire ; compensating means interposed between the elongated portion of the bead-seat and the cylindrical surface and in contact with them to compensate the differences in thickness present between the bead-seat and the tubular body ; said compensating means comprising an annular element that surrounds the tubular body and a seat which is afforded on the elongated portion of the bead-seat or on the part of the cylindrical surface of the tubular body facing the elongated portion of the bead-seat , the seat having an annular extension around the body and extending also along the direction parallel to the cylindrical surface for a preset length; said annular element being inserted in said seat and arranged in contact with the bead-seat and with the cylindrical surface ; characterised in that said annular element presenting one of its own surfaces facing inside the seat distanced by the bottom of said seat and said annular element projecting from the seat and sliding inside the seat , in a radial direction with respect to the body , towards the tubular body or towards the bead-seat so that, during use, the annular element moves from a more internal position of the seat to a more projecting position depending on the position of the rim so as to realise said compensation of the differences in thickness present between the tubular body and the bead-seat . a main tubular body extending around a rotation axis of the rim and having a cylindrical surface extending between two lateral edges and, in use, facing the tire ; a bead-seat having a greater diameter than the cylindrical surface of the tubular body and overlapped to it; said bead-seat comprising an external portion with respect to a space occupied, in use, by the tire and an elongated portion extending inside the space occupied, in use, by the tire ; compensating means interposed between the elongated portion of the bead-seat and the cylindrical surface and in contact with them to compensate the differences in thickness present between the bead-seat and the tubular body ; said compensating means comprising an annular element that surrounds the tubular body and a seat which is afforded on the elongated portion of the bead-seat or on the part of the cylindrical surface of the tubular body facing the elongated portion of the bead-seat , the seat having an annular extension around the body and extending also along the direction parallel to the cylindrical surface for a preset length; said annular element being inserted in said seat and arranged in contact with the bead-seat and with the cylindrical surface ; characterised in that said annular element presenting one of its own surfaces facing inside the seat distanced by the bottom of said seat and said annular element projecting from the seat and sliding inside the seat , in a radial direction with respect to the body , towards the tubular body or towards the bead-seat so that, during use, the annular element moves from a more internal position of the seat to a more projecting position depending on the position of the rim so as to realise said compensation of the differences in thickness present between the tubular body and the bead-seat . <EOS>