I've got a new single-speed Bianchi that has a flip-flop hub where the freewheel side (the side I actually use) is a Shimano SF-MX30 single-sprocket freewheel. That is, the freewheel mechanism is in the sprocket that goes on the hub, rather than being in the hub. Anyway, if you look on the net at a pic of this item you'll see that there's a really tight clearance between the part that spins (the black middle) and the part that doesn't spin when you coast (the silver sprocket). How do I keep that from gritting up and destroying itself? There's no seal there of course. Just a spinning metal piece and a stationary metal piece that almost touches.