Originally Posted by
DCB0
Any external mechanism can freeze up - derailleurs, cables, brakes, exposed IGH shift/cable attachment mechanisms...
On one somewhat cold ride years ago I had mud caked all over the drivetrain of my MTB and stupidly decided to dip it into a partially frozen over creek to clean it off... about 30 seconds later the rear mechanisms were encased in ice
For one winter I had a derailleur equipped mtb that I kept outside, and every morning I wold have to ride the first few miles in whatever gear I left it in the night before - usually a very slow climbing gear because I lived at the top of a hill. It would usually free itself up after a while, but not on the coldest (-30c) days.
My MTB has to be parked outside at work. Out of habbit I leave it in a easy gear in case it freezes up during the day. It happened once when forcasted snow turned into freezing rain which froze the derailleur solid. It did thaw up after 10-15 minutes of riding though.