A suspension system for a track vehicle, the suspension system comprising: a frame; a track surrounding the frame; a plurality of suspension modules resiliently interconnected between the frame and track to bias the track into engagement with a ground surface upon which the track vehicle sits; and at least one idler over which the track extends. Under a normal load, all weight of the track vehicle is borne by the suspension modules and not by the at least one idler. Under selected conditions the at least one idler bears at least some weight of the track vehicle to rigidify the track vehicle suspension during such selected conditions.