I am in the final stage of my build of my 84 Bianchi Special with a completely new modern groupset and came up on a problem... the front derailleur I got was a braze on (I could not find a clamp on at the time) so I purchased a braze on adapter (Shimano braze on adapter which comes in 31.8 mm in size but has 28.6 mm shim to fit the old school frames) which I've installed and it seem fine. I came upon a problem while I was adjusting the derailleurs. When it's in the small chain ring and biggest cog (ideal climbing gear ratio), the chain is rubbing on the inside part of the front derailleur and I can't seem to go in any further. After about an hour of adjusting/messing with the derailleurs, the distance that the derailleurs that needs to move is about the size of the shim. I am thinking the shim is pushing the position of the derailleur further out from the frame and this is causing the front derailleur to touch the chain. Did anyone experienced this problem before? If I changed out the braze on adapter which fits the seat tube size of 28.6 without the shim, would I have enough room for the front derailleur not to rub against the chain?