Bicycle Mechanics - FD question
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09-28-09, 07:18 PM
When I look at front derailleur options I see clamp on and braze on. To me, braze on applies to metal frames. My bike is a Giant TCR C1, when I look at the FD on my bike it is not a clamp on.
Is it a braze on that was epoxied to the carbon frame?
Is it something else?
If I want to change the drivetrain to......
SRAM from Shimano, what do I have to do?
How do I get the existing FD mounting bracket off?
Do I get a SRAM clamp on or a braze on and epoxy it to the frame?
09-28-09, 07:38 PM
As long as the large crank size is the same, you should be able to swap out the Shimano into a SRAM. Just undo the bolt that is holding the derailleur to the epoxied holder. Don't try to remove it from the frame, just attach the new braze on derailleur to the existing holder.
09-28-09, 07:39 PM
It's a fitting that accepts a braze-on style deraileur. On my carbon cervelo it's riveted on.
Don't try to remove it, you'll damage the frame. Get another braze-on style derailleur.
09-28-09, 07:39 PM
It is a braze on that is screwed into an aluminum "brase-on" derailleur boss that is seet into the carbon of the downtube when it was made. Unscrew it you will see what I mean.
I had a giant Cadex Carbon frame with one of these aluminum "braze-ons" for the front mech. You can't get rid of it without comprimising the frame. Get a braze-on derailleur and you should be fine, it mounts just like a braze on derailleur for a metal frame. I used a Braze-on campy mech with no problems. One of the good things about his method of attahing to frame is it eliminated the need to adjust the derailleur to line up properly. The bad thing is that it kinda limits the chainrings you can use to the most popular ranges.
09-28-09, 08:03 PM
Yes, technically "braze-on" applies only to steel frames. Some front derailers require a mounting bracket to be attached to the seat-tube. For steel bikes, this bracket is often brazed on. For aluminum, titanium, and carbon bikes, it is not brazed on, but the term "braze-on" is still used anyway. Wonder why they don't just say "bracket mount" or something.
09-30-09, 08:36 AM
Thanks for the help.
I have not investigated the exact method that the FD is mounted. By this, I mean that I have not looked to see if the bracket is epoxied to the tube of if there is some sort of bracket built into the frame to accept the bracket. But based on what I recall, I think that Gian simply epoxied the bracket to the seat tube.
If I assume that this is the case and thinking that removal of the epoxied on bracket will be difficult at best and result in lethal frame damage at worst. Will the Shimano Ultegra II bracket work for SRAM Red. Are the mounting points and screws the same?
09-30-09, 08:42 AM
You DO NOT want to remove the bracket from the frame. The "braze-on" style front derailleur is bolted to the bracket with a single allen head bolt and removal of that bolt frees the derailleur for replacement with what ever "braze-on" style new derailleur you want to use.
Gonzo Bob is correct that the term braze-on originally applied to steel frames but lingers on even for materials where the mounting bracket is welded, rivited or glued in place.
The downside to these brackets, however they are attached, is that they can limit adjustability of the front derailleur and may limit your choice of chainring configuration. They are essential on non-round seat tubes where a clamp cannot be used.
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