I’m looking for some help diagnosing a scary mechanical on my Canyon with only 630km on it. Everything was shifting perfectly until today when I dropped from the large to the small chainring. I felt a sudden jam, and the rear derailleur was pulled upward until it collided with the underside of the chainstay, damaging the frame.
The chain was slightly dirty but nothing extreme, and the bike hasn't been crashed. I’m wondering if this is "chain suck" despite the low mileage, or if my B-gap or chain length might be the culprit.
I contacted Canyon support and will also ask for advice to a trusted bike shop tomorrow.
The damage made to the frame doesn't look like the frame is toast, but I hope I get a replacement anyway. The bike is basically new.
Any advice on what caused this or how to prevent it from happening again would be massively appreciated.
by Kentiko
6 Comments
Were you backpedaling? This looks like the chain got jammed somehow and then some aggressive backpedaling pulled the derailleur.
This can happen if the chain gets shortened a lot very suddenly. Reasons why this might happen range from a stiff link to the chain getting derailed off the cassette or chainring and then getting picked up again. Backpedaling mid shift will also cause this to happen in certain circumstances. Without being there and witnessing the event. It’s tough to say if the bike is operating normally now.
How is the chain defying gravity in the first picture?
Probably has to do with that chain having the stiffest links of all time, looks like
I’ve seen pebbles get jammed in derailleur idler gears and cause this.
Loose chainrings and chain getting caught between rings? Or incorrectly mounted rings.
Chainsuck usually only happens when you use a worn chain on completely new chainrings.