Front Derailleur clamp sizes - can they be converted?

[malaholic]

I'm thinking of buying a new frame here soon and building it out with some of the components I already have. I know there will be some parts I'll need to buy (bars, saddle, pedals, etc), and depending on which frame I select I may need to pick up a different bottom bracket. I'm not sure about the front derailleur though. The one I have is a 31.8 clamp style. One of the frames I'm looking at would require a 34.9 diameter clamp; and one would require a braze-on style.

I'm wondering if my FD can be "converted" - if the cage can be mounted onto a different diameter clamp, if that makes sense. Or will I have to buy the entire assembly? (This is a SRAM Red FD, if brand makes a difference).

[lunacycles]

From what you are saying, you will not be able to use your current FD on the new frame. If you have a larger clamp diameter now than what you will need there are shims you can add to make it work with the smaller tube diameter . But you can't make a smaller diameter clamp work on a larger diameter tube, which is what you indicate.

You also can't do anything to make a clamp-on FD work with a braze on mount. You can take a braze-on front derailleur and attach it to a QBP "Problem Solver" so it acts like a clamp-on, but there is nothing I know of that will do the reverse.

[malaholic]

Thanks for the explanation! That's about what I expected to hear. Bummer, sounds like I'll need to get a new FD also regardless of which frame I choose.