Abstract: 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.