Originally Posted by Nasher
You can try putting a very slight chamfer around the leading edge to start them, but any more will effect the sealing.
Not sure the type the OP has, but the ones on my trailer have about 1/4" of surface that slip into the hub. Rounding or chamfering the edge to get rid of the sharp edge will not affect sealing at all.
When using them, don't go overboard filling through the grease nipple; I usually pump just enough to get the front spring loaded thing to move (though some bearing savers don't have the moveable plate part visible.)
As an aside, I saw a trailer on opening day of rockfish season last year - a 2-axle job - every hub had a different configuration. One had a bearing saver. The one behind it had nothing (castle nut and cotter pin exposed.) On the other side, one had aluminum foil wrapped around, fastened with a hose clamp. The last wheel had saran wrap held on with a rubber band. Didn't wait around to see what kind of boat was being carried. Moral of this story: Don't be that guy...