I'm converting a vintage steel frame to new drive train...and need some advice on how to deal with the front derailleur.

It currently has a braze-on Campy Record FD, meant for a 52/42 crank. I would like to use a compact 50/34, but even with the FD slid down to the lowest possible position, it can't grip the chain securely enough to upshift, without launching the chain over the outside of the big ring.

A braze-on Shimano Ultegra FD 6700 is readily available. The question is, what is the distance from the center of the crank to its proper position?

Presently, where the FD mounting bolt hits the bottom of the braze-on slot, it is about 145mm from the center of the crank.

Will the 6700 work? if not, is there another FD that might fit...or do I need to cut off the bracket?--or just give up on the compact crank?

Why not Fit a 52-36 so you leave the FD hanger on? 36 is only 2 t larger than 34.

I have an old 110 52t Campag outer from their old MTB cranks, so all 5 bolt holes are 110..

their new one is 1 , 112, & 4 110..

get a top swing derailer with a non-braze on clamp
maybe it clamps low enough that you can just ignore the existing braze on mount?

One more reason to not dedicate a frame to a spec. There have been a few ders which specifically were made to convert from a 52/3 BO position to a 50. IRD comes to mind.


One can file the BO slot lower if it's only a couple of Mms.


But the shifting issue claim makes me wonder about whether the full range of adjustments of the current der have been really explored. Andy

Have you looked at a triple FD? I only suggest it because of the cage size that may accommodate the 34/50 shifting better than an older double.

John

But the shifting issue claim makes me wonder about whether the full range of adjustments of the current der have been really explored. Andy[/QUOTE]

Andy, this inspired me to give the guides a tiny squeeze...works ok on the stand...we will see if it works on the road.

Without knowing any details of the vintage frame generally hacking off brackets from vintage frames is something best avoided, leave the frame as it is.

Andy suggestion of elongating the bracket holes seems excellent idea.

I came up with a different solution that completely solved the problem in a way that did not damage the bike, nor look stupid:



(Mine is sliver-colored.)

nice!!!

yup, tried it and lowered the rig about 2mm

I was trying to put a 46/30T on to replace a 52/42T. The braze-on bracket was too high, and the clamp-on couldn't go high enough. I finally had to shim the front derailleur to get it to work properly, but it was an ugly fix.

How about a Campy compact front der.?