A conveyor system has a pair of outer wheel tracks and a pair of inner wheel tracks, the wheel tracks of each pair being spaced from each other and extending parallel to each other. Each wheel track has at least one generally vertical portion and at least one generally horizontal portion. A conveyor member has two pairs of wheels, the wheels of each pair being located on opposite sides of the member, each pair of wheels engaging one pair of wheel tracks; the wheels and tracks are configured and oriented relative to each other so that the member is maintained in a selected orientation as the member moves relative to and along the tracks. The conveyor system includes a lift subsystem for preventing slippage of the conveyor member as the conveyor member travels around a curved portion of the conveyor system.