The present invention relates to a tension roller assembly configured for tensioning a belt of a belt drive, the tension roller assembly comprising: - a tension roller, - a pivotable support arm, - a tension arm comprising a compression spring configured to press the tension roller against the belt, wherein the spring extends between a first spring stop and a second spring stop and is maintained under compression, - a mounting plate, - an overcenter assembly connected to a second end of the tension arm, the second end being opposite to the first end, wherein the overcenter assembly connects the tension arm to the mounting plate, the overcenter assembly being configured to make a pivoting movement over a pivot trajectory between: a) an engaged position which is associated with an engaged state of the tension roller assembly, and b) a disengaged position which is associated with a disengaged state of the tension roller assembly, wherein the overcenter assembly further has a center position, wherein the tension arm comprises a rod which extends from the overcenter assembly to the support arm and through the rod guide, wherein the trajectory of the overcenter assembly between the center position and the disengaged position is divided in: a) a tensioned section, and b) a free-moving section in which the spring does not exert any force on the overcenter assembly.