A baler comprising: a frame; a bale-wrapping system including a surface-wrap guide roller; a counterknife assembly including a support member rotatably mounted to the frame and a counterknife arm (72, 94) mounted to the support member, the counterknife arm (72, 94) pivoting to cause a counterknife to cut surface wrap when the support member rotates with respect to the frame; a pulley member attached to and rotating with the guide roller; a traction device surrounding, at least in part, the pulley member; characterized in further comprising a tensioning assembly attached to the frame at a frame attachment point of the tensioning assembly, the tensioning assembly including a lost motion linkage limited by a stop to a limited range of motion with respect to the frame, the lost motion linkage being attached to a first end of the traction device at a brake attachment point of the tensioning assembly, and attached to the support member at the frame attachement point of the tensioning assembly; and a counterforce assembly attached to a second end of the traction device at a brake attachment point of the counterforce assembly, and pivotably attached to the frame at a frame attachment point of the counterforce assembly; wherein rotating the support member in a braking direction with respect to the frame causes the tensioning assembly to pivot in the braking direction to move the lost motion linkage toward the stop such that the stop prevents further movement of the lost motion linkage with respect to the frame, the tensioning assembly thereby applying a first tensioning force to the traction device, the first tensioning force being resisted by the first counterforce assembly, via the brake attachment point of the counterforce assembly, to impose a braking force on the pulley member via the traction device and thereby brake the guide roller; and wherein rotating the support member in a release direction with respect to the frame causes the tensioning assembly to pivot in the release direction to move the lost motion linkage away from the stop, the tensioning assembly thereby reducing the first tensioning force to reduce the braking force on the guide roller. a frame; a bale-wrapping system including a surface-wrap guide roller; a counterknife assembly including a support member rotatably mounted to the frame and a counterknife arm (72, 94) mounted to the support member, the counterknife arm (72, 94) pivoting to cause a counterknife to cut surface wrap when the support member rotates with respect to the frame; a pulley member attached to and rotating with the guide roller; a traction device surrounding, at least in part, the pulley member; characterized in further comprising a tensioning assembly attached to the frame at a frame attachment point of the tensioning assembly, the tensioning assembly including a lost motion linkage limited by a stop to a limited range of motion with respect to the frame, the lost motion linkage being attached to a first end of the traction device at a brake attachment point of the tensioning assembly, and attached to the support member at the frame attachement point of the tensioning assembly; and a counterforce assembly attached to a second end of the traction device at a brake attachment point of the counterforce assembly, and pivotably attached to the frame at a frame attachment point of the counterforce assembly; wherein rotating the support member in a braking direction with respect to the frame causes the tensioning assembly to pivot in the braking direction to move the lost motion linkage toward the stop such that the stop prevents further movement of the lost motion linkage with respect to the frame, the tensioning assembly thereby applying a first tensioning force to the traction device, the first tensioning force being resisted by the first counterforce assembly, via the brake attachment point of the counterforce assembly, to impose a braking force on the pulley member via the traction device and thereby brake the guide roller; and wherein rotating the support member in a release direction with respect to the frame causes the tensioning assembly to pivot in the release direction to move the lost motion linkage away from the stop, the tensioning assembly thereby reducing the first tensioning force to reduce the braking force on the guide roller.