Trashed my rear derailleur

My commuter bike had been shifting poorly all day, but I didn't pay much attention to it. On my evening commute, though, my chain made a sudden *crunch* noise and immediately my rear wheel skidded to a stop -- the chain broke and wrapped itself around the rear wheel, and my rear derailler was busted to shreds.

I noticed my derailleur hanger was bent in toward the wheel. That's probably what caused my poor shifting performance earlier, and it's probably what sent my derailleur into the wheel. Urgh.

I used my handy dandy chain tool to rig my chain for single-speed use, wrapping it around the granny gear inside chainring and one of the inside cogs to get some reasonable alignment. Because this is a newer bike with vertical dropouts, there's no way to adjust the chain tension. Hence, the chain sagged. A lot.

This instant singlespeed got me about a mile down the road when the loose chain skipped to the next larger cog. Pedaling became very stiff for about one revolution, then *snap* the over tight chain tension sheered all the chainring bolts clean off! I had never seen anything like that.

With a too-short chain and my small chainring done, I was dead in the water. I had to walk the rest of the way -- about three miles. Yay fun.

My bike rides Caltrain every day, and it gets beat up pretty badly with other bikes piled against it on a regular basis. I'm guessing the derailleur hanger probably got bent while on the train.

If your bike suddenly shifts poorly, check the rear derailleur alignment. It can save you from catastrophic failure. I'll need to see if I can straighten the derailleur hanger, or -- failing that -- buy a new one. The destroyed derailleur also needs replacement. Of course I'll need a new chain, possibly a new inside chainring, and certainly new bolts. I haven't examined the crank spider for damage yet.

Or I could just buy a new bicycle.

See related: bicycle, derailer, derailleur, repair, damage, parts, components