Originally Posted by
DX-MAN
Years ago, in Mountain Bike Magazine, Uncle Knobby's column was asked about these things; Knobby replied that they were called "Big Wedgies", all bike shops stocked them, all you had to do was go there and ask for one...lol!
They are there to keep the chain from destroying the spokes, should the chain fall into them. I don't see, and never HAVE seen, one of those saving a derailleur.
When I was riding a borrowed bike a few weeks back I discovered that the RD wasn't adjusted correctly when I shifted into the granny gear during a climb and realised I'd lost drive. It turned out the chain had fallen off to the inside of the largest cassette sprocket. No dork disk, apparently no damage to the spokes. It may just because I was lucky enough to realise something was wrong good and early, but generally speaking if you're going into the granny gear the chances are you're not going to be going very fast.
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