A belt tensioner system includes a belt tensioner and a bumper idler pulley. The belt tensioner includes an arm which is adapted to be rotatably-biased and includes a tensioner idler pulley which is supported by the arm and which travels in an arcuate path when the arm rotates. The bumper idler pulley is positioned at least partially in the arcuate path to stop the travel of the tensioner idler pulley when the arm rotates to a predetermined rotational position. In one application, the belt tensioner system is for an automotive vehicle.