I have a small amount of play in my gear cassette. It wiggles back and forth maybe 1/16". Is this normal? Also, I'm putting quite a few miles on the bike. How much play should there be in the chain, and how can I tell if it needs tightened? Last, the gears are dusty on the inside, the opposite side of the chain. Is it ok to spray water from a hose on this area, as it's very difficult to reach, or just leave it alone?