Broken Braze on - Repair?

trinewbie

Hey folks - A quick question...Essentially the braze on mount on my frame is broken and I am looking for a solution.

Frame is a cube 2007 GTC Agree (Similar to http://www.chainreactioncycles.com/Models.aspx?ModelID=30565) with a braze on Front mech adapter - Following a small a crash last year the front mech was twisted and smashed up, I replaced this , but at the time I noticed the braze on tab on the frame had a small bend and crack (obviously resulting from the crash).After a full inspection no structural frame damage was found. I thought originally that the braze on mount on the frame would hold as the crack seemed small. However, over time the crack in the tab has got worse from the force of shifting and at the weekend the tab bent completely out of shape and is now knackered.

Im looking for repair options - I assume is not possible to have another mount installed by a frame builder? I was thinking of asking the LBS to grind/ cut off the broken tab and use a braze on clamp adapter to mount the mech, but not sure if LBS will do this/ if there will be issues with structural integrity of seat tube if mech is band mounted, as frame is designed for braze on not band mounted mech.

Obviously if the tab was cut off there would be a small section of the tab left on the seattube - would this make using a clamp adapter difficult or would it just be a matter of using a slight bigger clamp?


Cheers
Trinewbie.

victorcarrera

If the existing one has pop rivets I would try grinding the heads off them and extract the rest through the top of the seat tube. Then replace with new braze on and pop rivets.
I don't see any propblem with using a clamp on there either. I am not aware that that part of the frame is any different for either type.

cdaly_

The usual procedure with pop rivets is to drill the heads out rather than grind off. It's usually a 5mm drill but if you're unsure of the size , start with a 4mm drill bit and then go up to a 5.

Still have to fish out the left-over bits of rivet though.

When drilling, you're probably best off having the seatpost out and the bike upside down so nothing falls down into the bottom bracket.

trinewbie

Thanks for the responses lads, tried a few bike shops yesterday who were unwilling to take on the job of removing pop rivets and braze on mount. Eventually found a private mechanic who will do the job for me and I will throw a braze on clamp adapter once done....thanks again,.

trinewbie

Mechanic has hit a problem, after removing the pop rivets it turns out the braze on tab is bonded to the frame....any suggestions>??

victorcarrera

trinewbie wrote: »

Mechanic has hit a problem, after removing the pop rivets it turns out the braze on tab is bonded to the frame....any suggestions>??

I didn't think they were glued on as well.
You are snookered then because the existing tab is in exactly the same position that you want the replacement to be.
Try to lever it off gently with a sharp chizel or similar. At best it may only damage the laquer coat. Otherwise if you want front shifting its a new frame.

trinewbie

Cheers -

I wasnt planning on putting on a new braze on tab, was planning on getting a clamp adapter so I can use the existing mech...Problem is that the biggest size I can find for a clamp is 34.9 (one of 3 standard sizes available). If I could get a non standard size, eg 35.5 that would allow clearance to clamp over the remainder of the old broken tab (with the mount part grinded off) this would solve the problem...If I could even find a clamp the could be adapted it could work....

If the mechanic cant get the tab off I will probably end up trying to adapt a 34.9 clamp to allow additional clearance, could be a pain in the @ss but better option than a new frame methinks....If anybody has any experience of this type of fabrication please let me know!

blorg

One option

Alternately, have you contacted Cube or the seller (CRC?) Some brands have a crash replacement policy where they will give you a discount on a new frame if you damage one in a crash.

steinone

Would an e-type front derailleur work on a road ring?

blorg

From the look of it I doubt it would clear road gearing, MTB front gearing is a lot smaller.