Any Wrenches?

[aicabsolut]

You can also see if there's a spec. sheet for your current bike on the web. It will generally tell you what derailleur it came with, including clamp size.

It does look like a clamp to me and not a braze-on. So that's step 1 out of the way at least.

[lunacycles]

I agree with Laura: it looks like this derailleur is actually a braze-on front derailleur attached to an after-market clamp (although the photo's really small, it's hard to be sure). I use these adaptors frequently to avoid the cheesey shims necessary to use Shimano clamp-on front derailleurs (that only come in 34.9 and 31.8mm diameters) on steel seat tubes (that are usually 28.6mm).

This is probably good news for you, if you are willing to buy a clamp in addition to the derailleur (or if the clamp comes with the derailleur and is the right diameter for your bike's seat tube). Google "Problem Solvers front derailleur braze on adaptor" and you will be directed to some online retailers that sell these clamps that are designed to accommodate braze on front derailleurs for all common size seat tube diameters. However, it may make more sense to just buy a new derailleur, as these adaptors run $15 or so, more with shipping.

errrr....never mind. I just re-read that the image is of your current set up, not of the actual derailleur for sale. So, never mind!!!