Bicycle Mechanics - "endless clamp" style braze-on front derailleur clamp?

I have a Vitus 979 frame. I'm having difficulty finding a decent 1.125" clamp front derailleur that will suit my needs, so I figured I'd just get a braze-on and use an adapter. I have a clamp that should work, but it's loose, so I think the seat tube is actually slightly smaller than normal diameter. Does anyone know of an "endless clamp" type of front derailleur braze-on adapter, sort of like the old SunTour front derailleurs?

Thanks

Pete

Sounds like you have Metric/French sized tubing @ 28.0mm vs. "standard" 28.6mm. Is your top tube 26.0mm (vs "standard"25.4mm) as well?
Some manufacturers made these slightly smaller clamp-on FDs back in the day, but it sounds like you're trying to use a more modern set-up.
Wrap some appropriately colored, or clear, vinyl tape around your seat tube.

Sounds like you have Metric/French sized tubing @ 28.0mm vs. "standard" 28.6mm. Is your top tube 26.0mm (vs "standard"25.4mm) as well?
Some manufacturers made these slightly smaller clamp-on FDs back in the day, but it sounds like you're trying to use a more modern set-up.
Wrap some appropriately colored, or clear, vinyl tape around your seat tube.

Vinyl tape is probably too squishy for a FD shim. I've used a short piece of PVC pipe to shim a front derailleur- it still works fine after several years.

For a real skinny shim try a piece of a plastic container or a thin piece of galvanized (less compression but might scratch frame)

Vinyl tape is probably too squishy for a FD shim. I've used a short piece of PVC pipe to shim a front derailleur- it still works fine after several years.

What schedule pipe did you use? Everything I see is way too thick.

What I'm suggesting as tape is the kind you would use for a chainstay guard.
Even Sch80 pipe would be too thick, irrigation grade pipe, whatever that stuff is called, might be good for adapting a 1 1/4 to a 1 1/8 or something, but that's just ghetto.

I had an '80 Motobecane w/Vitus tubing and it came stock with an alminum shim that went only half way around the seat tube. It was just on the backside of the clamp. I never had any slipping problems. The bike is long gone, so I can't tell you the thickness of the shim.

Yeah, I just measured the seat tube with calipers, and it's 28.1mm, with a French threaded headset (fortunately the frame came with a good Stronglight headset) and a BSC bottom bracket. Freaking French...

I was going to opt to shim it (probably use a soda can), but was looking at my market bike with an old SunTour front derailleur and wondered why nobody made a braze-on front derailleur mount in that style...maybe I'll email the guys at Velo Orange and see if they want to make one.

Thanks,

Pete

Yeah, I just measured the seat tube with calipers, and it's 28.1mm, with a French threaded headset (fortunately the frame came with a good Stronglight headset) and a BSC bottom bracket. Freaking French...


Wow. What year is your 979? Mine is from 1986 and uses standard 28.6 FD clamp and has standard 1" ISO headset/fork.

+1
Your's must be early production?
My Vitus 979 is also ISO fork BSC BB, 25mm seatpost, and takes a 28.6mm FD (Dura Ace mounted on mine).