An old bike of mine had a creak that I thought was coming from my pedals. Turns out it was coming from my rear wheel hub. I took apart the rear wheel assembly, cleaned out the cup, cone and balls, greased and reassembled. It appeared that the hub had gotten too tight. The creak was gone, but now its coming back. What would cause a wheel hub to go out of adjustment? Could it be the derailleur? The rear derailleur doesn't have an adapter, its just bolted onto the rear axle--it came that way. It has worked and while I've been meaning to get the part, it hasn't been a priority. Meanwhile, it shifts okay.