What's the difference in these front derailleurs? Why are they made differently? Is one better than the other? Can a braze-on be converted to a clamp-on?

Thanks,
velo

Braze-on style front derailleurs are made to mount to a metal tab built into the frame. In the case of a classic steel frame, this tab is brazed onto the frame, hence the origin of "braze-on."

Clamp-on have a metal clamp that wraps around the tube of a frame that doesn't have a built-in mounting tab for the front derailleur.

Braze-on derailleurs can be mounted to frames that don't have a mounting tab, using an adapter. The practical advantage of the braze-on style is that it allows the frame manufacturer to make a non-cylindrical seat tube if they want, or use a non-standard diameter at that point on the frame. Some would say it is more aesthetically-pleasing too. The drawback is that it limits the derailleur-positioning options more than a clamp-on derailleur, potentially a problem for those wanting unusually-sized chainrings.

I think, but don't know, that braze ons make for a few grams lighter front der mechanism. They're typically only found on higher end frames, and seem to be less and less common of late. I don't know why. I assume it's because it saves a little in production costs. Personally, I prefer braze ons

I suppose that a braze on could be converted to a clamp on simply by cutting off the tab, but what an awful thing to do!

Aside to mechBgon: from your previous avatar and your location, I assume you're a Cougar. I spent a summer in Pullman a number of years ago, before my cycling days. The palouse (sp?) country has got to make for some great riding.

Excellent guess, although actually that was intended to be a Wildcat, and a real Cougar avatar is still on my to-do list Yes indeed, I enjoyed many, many hours of riding in the Palouse while I was studying at WSU. The Lewiston Grade, Waiwai, Steptoe Butte, Kamiak Butte... and the highway to Spokane

In practice, for example, from 2003 Campa (in grams):

braze clip

91 104 Record
89 102 Chorus
93 106 Centaur

and so it goes.

Cheers...Gary

Braze on front mech fittings can cause heat and stress damage to very thin-walled steel tubing, and become a source of tube failure.

My Cannondale frame came with a clamp that accepts a braze-on derailleur.