kommisar

I am interested in either suntour symmetic or aero downtube shifters. These fasten on top of the downtube using a clamp band. The ones I see on ebay are for 28.6mm downtube. Is there a way to adapt them so they can be clamped on a 31.8 down tube?

clubman 

I'd guess not. Shimano made band clamps for 31.8 but Suntour?
If you were clever, perhaps you could McGyvor the two together. I don't have those skills.

JohnDThompson 

I seem to recall that the single top-mounted braze-on mount for these was pretty similar to a standard Campagnolo-style braze-on mount, maybe a bit of modification needed. Perhaps braze one onto a stainless hose clamp as @SurferRosa suggests above?

SurferRosa

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squirtdad

thank you, I just lost a fair amount of a nice IPA

Rooney 

I currently have a front derailleur attached to an endless band clamp going around the 31.8mm seat tube of my Cannondale ST1000 . I'd assume that would do the trick, no?
Originally attached to a Suntour XCD front derailleur, now hooked up to a Shimano Deore LX fd. No modification necessary to swap the two.

clubman 

I though I found one on ebay but it's not the endless band clamp.

I've got a Shimano Exage 31.8 in the stash. When I get a spare moment, I'll see if 'I can mate my snake with this chicken' (name the film)

clubman 

The Shimano endless band clamp is entirely different from the band clamps used by either the Symmetric shifters, or the earlier 28.6 Suntour FD's (Cyclone, Superbe etc) Different designs including bolt size and 'fixing plates' for the lack of a proper name. The Suntour clamp overlaps a plate and bolt tensioner while the Shimano remains open ended and uses a spring, bolt and a tabbed plate to hold the gear in position. The 2 ends of the clamp don't actually meet, so it only resembles an endless clamp. Incompatible, at least the 80's versions.

I'd be interested to see how these could by mixed together and remain functional.

Rooney 

Welp. I’m mixing up my front derailleurs. I’d swapped a Deore with a Deore LX. The Suntour XCD entered the mix for a minute when I’d thought I could put it on the ST1000, but realized its integrated clamp was too small. I must have confused things in my head after all the shuffling around of parts. It doesn’t help that the rd on that bike is Suntour and looks close enough to the LX that I thought I had two Suntour derailleurs on there. My bad!

Schweinhund

Not an out of the realm of possibilities idea. A long clamp with just enough solid band that you could cut and use ye olde dremel to make the necessary mods.

clubman 

I admire courageous attitudes but these clamps assemblies were high end imo. I've had great success dialing these in as easily as I scratched some seat tube paint.

79pmooney

I don't see why this isn't doable. Any nut compatible with that bolt through the shifter could be mated to a SS strap to handle any tube diameter. (I have the Superbe similar shifter (no, not auto-trim and a different bolt diameter) mounted on a "braze-on" the builder made for me on my first TiCycles.

So a crude version could be a SS pipe clamp with worm-drive tightener. Put the worm drive under the DT. Kink the strap up at the nut, over the top, down and back to the worm drive. Slide the box over, insert bolt and tighten. Better, if space allows, would be to wrap around both nut and strap tightly with thin wire and solder. That would stop the strap from trying to spread and lift the box.

Yes, just thinking out SurferRosa's idea a little more. And not being willing to dismantle the shifter that's been on one of my (braze-on free save for the stop under the DT) bikes for years.

clubman 

I'm just a user, not a design guy but the tolerances allowing that band clamp to secure the gear to the tube seem very refined. I've mounted and remounted at least a couple of dozen of these clamps over the years.