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Old 03-06-11, 01:06 PM   #1
Campag4life
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Down Tube Cable Stop bracket came loose on carbon fiber frame....

I am in much need of some technical advice as I have at long last solved my shifting dillemma which has left me with another issue to resolve.

Please see pics of the downtube of my 2006 Look 555 frameset just aft of the head tube. Notice the bracket that secures both derailleur cable stops to the underside of the downtube has come loose. The glue bond with the carbon fiber down tube is broken and the cable stop bracket is gapping and rotating depending on what chain ring I am on in front due to change in cable tension from the front derailleur.

The metal rivet shown is still in place and the only thing keeping the cable stop bracket attached to the down tube albeit not securely enough for position shifting.

Therefore I need some repair advice from those with experience...maybe some have even performed this repair on a carbon fiber frame.

A couple of ways to proceed:

Approach 1:
Quick and dirty...would be to wick some lower viscosity super glue into the void between bracket and downtube afforded by the slightly elongated rivet and then clamp the bracket down to the downtube until glue has dried...I could fashion a simple clamping fixture until the glue sets. Problem with this approach is good or probably uneven glue penetration however

Approach 2:
The best approach may be to drill out the metal rivet. Removed the bracket and apply glue to both the underside of the bracket and the interfacing bottom down tube surface and again clamp until dry. Then install a new rivet for further security.

My quesitons are...which approach or perhaps another would you suggest?

What kind of glue do you suggest?...epoxy?...super glue?....Gorilla glue gel?

If I install a new rivet, how do I figure out the proper replacement rivet length/clamping zone?
Any tricks for drilling out the rivet without having the rivet shank rotate while drilling since I can not retrain it from inside the tube?

Thanks for any advice you could provide. I am a DIY'er by nature and would like to avoid shipping the frame off to a builder or back to Look for repair if possible.

I appreciate your help.




Last edited by Campag4life; 03-06-11 at 01:11 PM.
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Old 03-07-11, 05:32 PM   #2
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I guess you guys don't do carbon.
Carry on....lol.
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Old 03-07-11, 07:14 PM   #3
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you're right, not much carbon going on around here. I'd use an epoxy. I've had enough issues with super glue that I wouldn't trust it. Drilling the rivet seems to be rife with problems. Sneak some epoxy underneath and clamp it, making sure not to starve the joint or crush the tube
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Old 03-08-11, 04:59 AM   #4
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Originally Posted by unterhausen View Post
you're right, not much carbon going on around here. I'd use an epoxy. I've had enough issues with super glue that I wouldn't trust it. Drilling the rivet seems to be rife with problems. Sneak some epoxy underneath and clamp it, making sure not to starve the joint or crush the tube
Thanks unterhausen. I sent an email to Look USA...and no response so far. Don't believe they would consider warrantying the frame...its a 2006 and not sure if they do repairs...likely not.

I sent an email to Calfee who is regarded as the premier carbon fiber repair shop in the country...out in California. I contacted them for advice mainly as I want to take this on myself...asking them for any tips they could provide as I didn't want to ship the frame off if possible and for expediency would prefer to do it myself.

Their response was precisely the same as yours. They suggested that re-riveting the bracket could be problematic and suggested to sneak some JB Weld under the bracket and clamp it lightly. So that's what I am going to try. I will remove the fork but now don't have to remove the crank which makes me happy as I just had it off for service this winter.

Repair Plan:
- Completely mask off entire area adjacent to the bracket.
- Mix 2 part slow set (regular) JB Weld...which is an aluminized epoxy.
- Partly fill 10 ml dispensing syringe
- Inject epoxy under bracket gently lifting it on each side of the rivet for access.
- Probably use 1 or 2 cable ties to shore up the bracket to the down tube.
- Wipe off squeezed out epoxy due to clamping.

Believe this will fix it and my thanks for your response.

Last edited by Campag4life; 03-08-11 at 05:03 AM.
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Old 03-08-11, 12:34 PM   #5
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Epoxy definitely. But it should be the good stuff. I don't use JB weld, but if Calfee says so. I use WEST, 105 for anything heavily loaded. Be very careful about how you clamp it. Epoxy actually likes a gap. On the other hand it will be less loaded the closer in it is mounted to the tube. Just don't clamp it so hard you take the epoxy out. Also,if during clamping you slack off for an instant, clamp wobbles, you should start from the beginning and refill with glue. When you look at how cleanly that is separated it quite likely was glue starvation. The other main candidate is contamination. Gently scuff sand. Wash with alcohol before bonding. Do not use acetone. Do not get your fingerprints on the contact surfaces after cleaning.

Last edited by NoReg; 03-08-11 at 12:38 PM.
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Old 03-08-11, 01:59 PM   #6
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Originally Posted by Peterpan1 View Post
Epoxy definitely. But it should be the good stuff. I don't use JB weld, but if Calfee says so. I use WEST, 105 for anything heavily loaded. Be very careful about how you clamp it. Epoxy actually likes a gap. On the other hand it will be less loaded the closer in it is mounted to the tube. Just don't clamp it so hard you take the epoxy out. Also,if during clamping you slack off for an instant, clamp wobbles, you should start from the beginning and refill with glue. When you look at how cleanly that is separated it quite likely was glue starvation. The other main candidate is contamination. Gently scuff sand. Wash with alcohol before bonding. Do not use acetone. Do not get your fingerprints on the contact surfaces after cleaning.
Thank you....great advice. The joint failed because it had some help ...frame fell from a wall stand and apparently the cable stop caught on something as shown by the mark on it. I was trying to set up some new shifters and couldn't figure out why I couldn't maintain rear derailleur adjustment and finally discovered the issue.

Starving the joint for the repair is the same point that underhausen made which is something I didn't know but makes perfect sense. I will use a single tie wrap to draw the bracket down with an eye toward keeping a film thickness of epoxy between the frame and down tube for best strength. I am pretty confident this repair will be plenty strong and thanks again.

Last edited by Campag4life; 03-08-11 at 02:05 PM.
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Old 03-23-11, 02:40 PM   #7
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+1 for real epoxy and +1 to scuff sand.

mask everything you don't want epoxy all over.

did you fix this?
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