John has left a new comment on your post "Dork disk":
I've seen a chain come off with one of these things fitted, the disk got ripped to shreds and made it harder to get the chain back out of the wheel.
And it's not just bad adjustment that causes it to come off, bent hangers can cause it too.
Posted by John to Cyclelicious at 10/27/2008 03:36:00 AM