A track drive system comprises a chassis frame and a drive wheel rotatably coupled to the chassis frame. An upper idler is rotatably coupled to the chassis frame rearwardly of the drive wheel. A forward idler is rotatably coupled to the chassis frame below the drive wheel. A suspended frame is pivotally coupled to the chassis frame by upper and lower swing arms. A rear idler is rotatably coupled to a rear portion of the suspended frame at a location displaced generally downwardly from an attachment point of the upper swing arm by a rear idler offset distance. A lower idler is rotatably coupled to a forward portion of the suspended frame. A biasing means biases the suspended frame away from the chassis frame.