A motor vehicle reinforcing structure includes an instrument panel crosspiece (1) fixed between the left and right front pillars (2) of the vehicle, and a hollow tube (7) having a length substantially less than the instrument panel crosspiece (1) and substantially parallel to the instrument panel crosspiece, and the hollow tube (7) being fixed to an end portion of the instrument panel crosspiece (1). The hollow tube (7) is rigidly fixed to the instrument panel crosspiece by first and second linking elements (8, 9) so as to form a quadrilateral therewith and through its end proximate the end of the instrument panel crosspiece (1) to the pillar (2) adjacent the vehicle by a threaded element (20) whereof the axis is parallel to the axis of the hollow tube (7) and is inscribed in an inner volume of the hollow tube (7).