Rear Derailleur broke off when I shifted too low gear?? Specialized 29er hardrock SE, 7 speed 34-11 cassette, Shimano tourney rear derailleur. I converted the bike to electric with a Bafang 750w mid-drive kit which replaces the 42/34/24 chainring with a single 46 tooth sprocket. I did not change the chain. I have been riding it a while without issue (love it) but seldom use low gear. I was going very slow around a bunch of people at an outlook and when I shifted to low; the derailleur just snapped off. I'm thinking the chain length may be marginal with the larger front sprocket??? Would a 7 speed internal rear hub be a better option than a new derailleur?? What would be a good replacement??