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On a scale of fixeable to Dimond how fucked is my bike
Just riding along on the weekend and noticed my front derailleur wouldn't shift into the big ring. It was almost as if the cage separated and wasn't pulling the chain. I stopped to assess and noticed the epoxy holding my front derailleur mount to the frame had come away and also pulled the rivet through the carbon. It's a 2010 Scott Plasma, Scott's website says frame warranties are 5 years. It's also second hand. I've reached out to the original owner to see if he has the original receipt, and then I'll try and contact Scott to see what they can do for me.
Apart from that, what's anyone elses take on this? I was going to drill out the rivets, remove the mount and assess the damage more closely but I'd rather not do that until I hear from Scott. To me it's a clear manufacturers defect. There's no sign of any corrosion on the rivet. To me it can either be two things, improper installation of the rivet which wasn't brought to light because the epoxy held, or delamination/corrosion of the carbon/aluminum intervace causing the rivet to pull through.
I found a few articles online with similar issues on other bikes with how-to's on repair. Basically re-riveting with a larger/different type of rivet. My other issue is, and I won't know until I inspect it, is more delamination of carbon around that area. Simply re-riveting and re-epoxy will still leave the underlying problem of delamination, if that's what caused it.
Comments
(Thank you for reinforcing my fear of all that is carbon on bikes.)
Is the down tube a funky shape? Wondering if a clamp on hanger would be a cheap/temporary fix.
I think it's more of a case of "it can be repaired correctly and never be an issue again by someone else, or it can be hacked and have a 75% chance over never being an issue if i do it"
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I think the main failure, however, is the design. The derailleur hanger is only mounted using two small 1/8" rivets, one of which wraps around the seat tube and connects on the edge (the one that pulled out).
The mount, and derailleur, wants to be straight, because, but the rivet it forcing it closed. I think even if I repair it identical to new the same issue could come up in the future.
The option I'm exploring now (unless Scott decides to warranty the frame) is to use a different derailleur mount. Basically I'll remove the old mount and use a different one. One that doesn't apply force on the edge of the seat tube, like this. http://soshanger.com/epages/box11137.sf/en_GB/?ObjectPath=/Shops/box11137/Products/"WG39/GNT"
To do this, I'm not sure if I should build up an extra layer of carbon or not. It's easy enough to fill the old holes with some epoxy but I'm not sure how built up that area is. If I go with a new mount there's a possibility that the new holes will also pull out which could be catastrophic since it would basically pull away the carbon with it. Adding some extra carbon is probably the safest route to prevent this but is a lot more time consuming. The other issue is that most derailleurs don't use the standard rivet system, they screw into a rivnut mounted in the frame. Right now I don't have the tools so install a rivnut, but I can work that out. The bonus is that the area for repair doesn't have any decals/paint so once completed it should look like new. I'll keep everyone updated.
Also, if you do have a failure of your repair on the original clamp design, you still have the 1x back-up. If the re-design fails, you're probably looking at a new frame.