kcroley

I have a vintage Nishiki Olympic that I'm rebuilding, and need a clamp-on front derailleur. I'd like to find an older Shimano Dura-Ace (FD7400??) clamp-on that will fit, but my downtube width is 26mm. Are there any Shimano FDs that fit that tube size? Would a shim work for a 28.6mm clamp-on?

Thanks!

Lascauxcaveman 

I think you mean your seat tube is 26mm? (The downtube is the one that runs diagonal from the head tub to the bottom bracket).

And yes, you could shim it with something; a triple wrap of beer can aluminum, cut to fit the width of the clamp might do it, or similar cut from a laundry detergent bottle or some other HDPE container could work for you. I've done the beer can shim on seatposts (didn't work very well) and handlebars (worked great).

Another possible route you could take is get one of these shims, and a shop for a nice FD with a 31.8 clamp size, which is quite common. Such as Dura Ace 7700 or 7800. I don't know if that would require a narrower 10-speed chain though. And it's kind of high-end, pricey stuff for an old hi-ten framed bike. If was shopping in your situation, I'd probably be looking for a deal on a SunTour Mountech or Cyclone derailleur, then make a shim to fit it. The performance is as good and it'd be less expensive than the famous name stuff.

kcroley

Yes, you're right, I meant the seat tube. Are there aftermarket shims that can be bought at the correct size?

fietsbob

Nah , Question your Measurements ..
Asian Bikes used British tube standards which are Inch Based seat tubes are Typically 1.125" aka 28.6mm in metric equivalencies.

Its the French that built themselves out on a Limb by insisting standards be fully Metric.

zukahn1 

This bike should take a standard 28.6 clamp type front derailleur. 26.0 is the inside seatpost diameter the outside diameter on the tubing is a standard 28.6 so 7400 series clamp type DR will work fine no shim needed.

kcroley

OK, 28.6 it is, and I'm locking in on a Shimano Dura-Ace 7400 clamp-on. Thanks for the help.

Lascauxcaveman 

lol, i thought it sounded fishy, but I had an old Monkey Wards rattletrap pass through my hands once that had crazy skinny tubes, so I thought, "well, maybe."