During shipment, the spoke(s) on the fan frame may be slightly bent forward or backwards, causing a wobble when the fan spins. The spokes are the square tubing pieces that are welded onto the center hub plate. Each fan blade is screwed onto a single spoke.
These are the steps to remove any wobble:
Stop the fan from spinning.Make sure the hub is fastened tightly to the hub plate.Spin the fan by hand slowly, while looking at the fan blades from the side view to determine which spokes need adjustment.Gently push (to the front) or pull (to the back, towards the tail) the needed spoke(s) into alignment, until the wobble is eliminated.