A sheet feeder (1) having a stack hopper (9) for holding a stack of sheets (8), and feed belts (5, 6, 7) for advancing the bottom-most sheet from the stack, has traction belts (110, 111, 112) between the feed belts. The traction belts extend around a shaft (25) beneath the hopper and around a shaft (27) positioned intermediate the reach of the feed belts, a short distance short of separators (30, 31). The traction belts are preferably thicker than the feed belts and textured on their outer surface.