I took my partners bike chain off to clean as it was caked in solid grease. I left it in some thinners for a few hours. Scrubbed all the grease off. Then re oiled and put it back on. Went for a test ride and then t felt great. Changed gear a few times and all was well. Then suddenly the chain came off and the bike seized up. One of the jockey wheels has broken and the rear mech is completely bent in the wrong direction. Any ideas why this happened?
by Only-Dealer-8583
2 Comments
Does your partner often shift gears as they ride? This sounds like a bent derailleur hanger which when you shifted to the lower gears it somehow got caught in the spokes. It has happened to me and is more likely to do this damage than an incorrectly routed chain. This wouldn’t have happened to your partner if they don’t shift often but was likely just a bomb waiting to go off
There is no way simply cleaning and lubing the chain would cause this.
In several of the pics (especially the last one), it looks like the chain is routed from the bottom pulley and directly to the cogset. In other words, it seems like **the chain completely bypassed the upper pulley, which isn’t good.** [This is how the chain is suppossed to be routed.](https://images.ctfassets.net/enhz2tloa31p/3d3ft0csIAlm4bCmN0NGxI/48ba5649007f7ab5be166c1f1c111da3/img_-_UM_-_Chains_-_Chain_Install_-_Non_Cage_Lock_-_1.jpg)
I know it’s hard to tell from the pics. If you want to be sure, just bend the derailleur cage back so that it is roughly in the same shape and position as it was before (it’s not like you can hurt the derailluer or chain any worse. That way we have a clearer idea how the chain was routed.