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Old 02-16-08, 01:43 PM   #1
foul smell
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Is there a way to mount a derailleur on a carbon frame with no braze on mounts?

I bought an ultra cheap carbon frame. Its a Giant brand but I didn't notice it until now...there are no braze on mounts for the carbon bike. I think this is a "second" frame I bought since it was so cheap. Is there any way I can have a bike shop put in a braze mount on this carbon frame?
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Old 02-16-08, 01:45 PM   #2
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You can buy a clamp that will adapt a braze-on FD.

Just get the diameter of the tube and buy the right clamp.

If you're just asking if it is possible, then yes, it is.
If you're asking whether most shops would perform the work, no.

I know I wouldn't for a customer due to liability issues, but I might on my own bike.
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Old 02-16-08, 02:04 PM   #3
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You can buy a clamp that will adapt a braze-on FD.

Just get the diameter of the tube and buy the right clamp.

If you're just asking if it is possible, then yes, it is.
If you're asking whether most shops would perform the work, no.

I know I wouldn't for a customer due to liability issues, but I might on my own bike.
he's right,..to "braze-on" anything on a CF frame would require first finding or fabricating the derailleur hanger mount, then stripping the clearcoat and epoxy "gel coat" on most of that tube, and then re-laminating CF matting with the hanger in place, then vacuum bagging and heat cycle curing to set the carbon/epoxy composite.
plus it'll look lumpy because you added CF matting to the surface of the tube, and had to laminate it in, so your tube will have a big bulge in it where the mount is.

at best it works killer, at worst the entire tube has a catastophic failure, and theres really no way to know without doing it.

the clamp on hangers work fine, and I think you can get trick looking CNC milled ones for not that much $$$. OBVIOUSLY get the size correct, and do not over tighten or you could crunch that tube.

if you pay me ridiculous amounts of money and name several children after me, I'll make you a custom carbon fiber derailleur clamp on hanger.

(I work as a plastics fabricator)
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Old 02-16-08, 11:27 PM   #4
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Last Giant I looked at, the derailleur clamped to the frame. Just something they do....
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Old 02-17-08, 05:40 PM   #5
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so it is acceptable to use a clamp on derailleur on a carbon frame?
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Old 02-17-08, 05:47 PM   #6
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so it is acceptable to use a clamp on derailleur on a carbon frame?
Yes, done all the time. Don't try to see how tight you can get the clamp bolt but otherwise it's just like mounting a clamp-on fd on any other frame material.
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Old 02-17-08, 06:08 PM   #7
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so it is acceptable to use a clamp on derailleur on a carbon frame?
Highly recommend using a torque wrench for this.
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Old 02-17-08, 07:05 PM   #8
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Highly recommend using a torque wrench for this.
how about "if you don't use a torque wrench you might just ruin the frame"

like I, and everyone else said:

1) get the correct size clamp
2) get the torque specs from the frame manufacturer. (if giant does this all
the time, they will have accurate TQ specs for their CF frames)
3) use a quality beam* style wrench that'll read inch pounds

*beam style TQ wrenches are better for fine-light work,(IMO) because you can see the gradual progression so you can control the tightening more accurately: with a clicker you just crank and crank and than "pop!" you get the click, but there's no warning, and you can't see how much force your applying until it pops.
again this is my subjective opinion, but it works for me, and has through many many years of wrenching on the various vehicles I own.
I use clickers when you can't see the dial face, or when you are torquing many fasteners in sequence (like cylinder heads on a car)
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Old 02-17-08, 07:30 PM   #9
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Get one of these. It'll set you back a Benjamin but it only weighs 7grams

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