Abstract: A tension roller with eccentric internal pivot and a tensioning device consists of a cylindrical roller having a shape adapted for each type of transmission housing one or several roller bearings, which are integral with a hub including a large base plate pivoting about a fixed axis. The eccentricity between the fixed axis and the axis of rotation of the roller enables, by the pivoting of the device about an axis, to cause the roller to travel along a circular path, with an amplitude twice the value fo the eccentricity, which provides the tensioning stroke of the transmission. The flange, housed in the hub, in its central part, is actuated by the screw clamping the device on the bearing surface. The hub may comprise one or several driving arms which enable to simultaneously exert and measure the tensile load of the transmission, using standard clamping tools available off-the-shelf.