My most unexpected mechanical was my rear derailleur snapping, right in the middle of the alloy casting, while just spinning along on the flat, no gear changing, nothing. Just riding along, and…BANG!!
Thankfully I was riding a Ti frame and had a 32 spoke rear wheel. The damage was zero to the frame and the spokes were not too bad really. The mech hanger was obviously fine since it was the mech that snapped off half way up!
I was about 25 miles from home with no hope of rescue, so I split and shortened the chain, tied the mech onto the chain stay with a zip tie and rode home single speed.
I had intended to write to Shimano but I couldn’t be bothered with the irritation of most likely being told it was just normal wear and tear/user error/wrong set up or some such excuse.
