Paulcomp has axle keepers that push from the crank side of the drop outs. Today I saw a bike with some axle keepers that slipped around the drop outs and had a screw that pushed from the back side of the drop outs. First, does anyone really need axle keepers for general street use? Second, if so, which side shoud they push from? It of course seems like the paulcomp ones are good to keep the chain from getting too much slack, and the other ones would keep the chain from getting too tight. I don't see that very many people use either.