Sub-assembly for a bicycle rear wheel, comprising a sprocket-carrying body and a cogset mounted coaxially on the sprocket-carrying body through shape engagement of the cogset on a coupling profile formed on the radially peripheral surface of the sprocket-carrying body and extending in the axial direction, wherein the following transversal planes are defined, perpendicular to the common axis of the sprocket-carrying body and of the cogset: abutment plane of the sprocket-carrying body: plane at the axial abutment position of the cogset on the sprocket-carrying body; outer bulk plane of the sprocket-carrying body: plane at the end of the sprocket-carrying body opposite to the abutment plane; outer bulk plane of the cogset: plane at the outer face of the smallest sprocket, facing the opposite way with respect to the cogset; inner bulk plane of the cogset: plane at the inner face of the largest sprocket, facing the opposite way with respect to the cogset; wherein - when the cogset is mounted on the sprocket-carrying body - the following lengths are defined, in the axial direction: Lc: length of the sprocket-carrying body, between the outer bulk plane and the abutment plane; Ls: axial length of the coupling profile on the sprocket-carrying body; Lp: length of the cogset, between the outer bulk plane and the inner bulk plane; Sint: inner overhang, equal to the distance between the abutment plane of the sprocket-carrying body and the inner bulk plane of the cogset, positive if the first is outside the second; Sest: outer overhang, equal to the distance between the outer bulk plane of the sprocket-carrying body and the outer bulk plane of the cogset, positive if the first is inside the second; characterized in that the following adimensional indices are calculated: P 1 = Ls / Lp P 2 = Lc / Sint + Sest K = P 1 * P 2 where K is comprised between 2 and 4. wherein the following transversal planes are defined, perpendicular to the common axis of the sprocket-carrying body and of the cogset: abutment plane of the sprocket-carrying body: plane at the axial abutment position of the cogset on the sprocket-carrying body; outer bulk plane of the sprocket-carrying body: plane at the end of the sprocket-carrying body opposite to the abutment plane; outer bulk plane of the cogset: plane at the outer face of the smallest sprocket, facing the opposite way with respect to the cogset; inner bulk plane of the cogset: plane at the inner face of the largest sprocket, facing the opposite way with respect to the cogset; abutment plane of the sprocket-carrying body: plane at the axial abutment position of the cogset on the sprocket-carrying body; outer bulk plane of the sprocket-carrying body: plane at the end of the sprocket-carrying body opposite to the abutment plane; outer bulk plane of the cogset: plane at the outer face of the smallest sprocket, facing the opposite way with respect to the cogset; inner bulk plane of the cogset: plane at the inner face of the largest sprocket, facing the opposite way with respect to the cogset; wherein - when the cogset is mounted on the sprocket-carrying body - the following lengths are defined, in the axial direction: Lc: length of the sprocket-carrying body, between the outer bulk plane and the abutment plane; Ls: axial length of the coupling profile on the sprocket-carrying body; Lp: length of the cogset, between the outer bulk plane and the inner bulk plane; Sint: inner overhang, equal to the distance between the abutment plane of the sprocket-carrying body and the inner bulk plane of the cogset, positive if the first is outside the second; Sest: outer overhang, equal to the distance between the outer bulk plane of the sprocket-carrying body and the outer bulk plane of the cogset, positive if the first is inside the second; Lc: length of the sprocket-carrying body, between the outer bulk plane and the abutment plane; Ls: axial length of the coupling profile on the sprocket-carrying body; Lp: length of the cogset, between the outer bulk plane and the inner bulk plane; Sint: inner overhang, equal to the distance between the abutment plane of the sprocket-carrying body and the inner bulk plane of the cogset, positive if the first is outside the second; Sest: outer overhang, equal to the distance between the outer bulk plane of the sprocket-carrying body and the outer bulk plane of the cogset, positive if the first is inside the second; characterized in that the following adimensional indices are calculated: P 1 = Ls / Lp P 2 = Lc / Sint + Sest K = P 1 * P 2 where K is comprised between 2 and 4.