See the clear disk on my rear axle? Bet you didn’t know this particular piece of gear has a nickname. It’s called a “dork disk.”
Bet you don’t know why.
Well, if you are a serious cyclist you probably do know why and if you’re not one, you probably don’t care. But I’m going to tell you anyway.
The purpose of the dork disk is to prevent the chain from flying off your inside gear sprocket and slamming in between the spokes of your rear wheel. Should this happen, several unfortunate events would occur including (but not limited to) the destruction of many of the wheel’s spokes and probably the wheel itself, and a sudden complete stoppage of forward momentum – except of course for the rider who will continue to experience whatever forward momentum he/she enjoyed prior to the destruction of the rear wheel, meaning the rider will be catapulted forward to an uncertain (but probably unpleasant) future.
This seems like a good reason to have this gear on your wheel axle, but the cycling elite will quickly point out that the only way for a chain to jump the inner sprocket as described above is for the bike’s rear derailer to be improperly adjusted. And only a dork would allow that to happen. Thus the name.
That all seems perfectly rational, but I’d rather keep the disk on my wheel to prevent that sort of occurance. If this means the occasional super-cyclist who flies by me at mach speed considers me to be a dork, I believe my ego can take the punishment.