Take yer tire off and scope it out. Wiggle the axle and see if there's any slop. If there is, you can try new axles and bearings. Still might require a small washer to shim it. If it does, make sure there's no bind when the wheels tight. May have to use locktite and leave the nut backed off a bit to get it perfect. After a little bashing, it may need tightened a tad.