A baler including a plurality of endless belts and opposing side walls defining therebetween a chamber for receiving forage material and forming a bale. Each of the belts is formed as a full width belt extending substantially a transverse distance from one of the side walls to the other of the side walls. In order to maintain proper tracking of the full width belts, a drive roller for each of the belts is formed with a sleeve centrally located on the drive roller and defining a crown for the roller, as well as improving traction between the roller and the belt. In addition, each of the full width belts is formed with a differential stiffness wherein the belt exhibits a greater stiffness against bending about an axis perpendicular to the rollers than the stiffness against bending about an axis parallel to the rollers. In order to facilitate removal of debris from an area adjacent to an inner surface of the belt, a roller for guiding the belt is provided with a helix structure wherein the helix acts as an auger to convey debris away from the center and toward the ends of the roller.