Clamp-on FD question
 

Will a 31.8 clamp-on FD fit onto my 30mm o.d. seat tube?
If not, does anyone sell a shim...or do I fashion my own?

(These early 70's Schwinn Super Sport rebuilds are causing me more than a few sizing headaches!)

I bought a huge roll of shim stock from mcmaster.com. I'll be happy to cut you a piece if you like. This should last me a lifetime. You might be able to make a shim with a beer can. The material is very thin, and you can cut it with scissors.

The shim stock I bought is .02" thick, 6 inches wide, and 100" long. It cost me $12.17.

LINK

The nominal shim thickness needed by the OP is 0.9mm or approximately 1/32". Hardware stores probably have sheet aluminum around this thickness, might charge several dollars for it though.
1-1/2 wraps of 0.020" shim should work also. Lots of options.

Thanks for the kind offer, Tom, e-mail has been sent.

I guess I shouldn't be turned off by the beer can method. Although rudimentary' it is probably effective. I'm growing weary of hunting for 21.1 long-throw quill riser stems and 30mm seat post clamps!

I've read about using scotch tape...is that valid for some applications, or total hokey?

I wouldn't use anything that soft (except as a temporary stopgap). It will tend to compress over time and lose preload.

In my experience with the Schwinn fillet brazed seat tubes, I just went smaller, forced the band wider, and added a longer clamping bolt as needed.

What type of FD are you using?

I got curious and measured a coke can. .1 mm or .004 inches. Sounds like it's too skinny for your project. Real shim stock would be better here.

Scotch tape probably won't work unless it's built up to many layers. I've had good luck using a paint on layer, or two, of liquid plastic. Plastidip. More to protect the paint than build up thickness but the stuff is quite thick and could work for you if a few coats are used.

Oh, and, if Tom's kind offer turns out to be too thin for you, lemme know. I have shim stock in several thicknesses and could cut you a piece. Mine is brass.

Thanks for the offer, rootboy, I'll keep it in mind.
Pastor, I'm hoping to use a Shimano Tiagra on my son-in-law's SS, but I've yet to find a clamp-on in my size. For my orange SS I've collected a group of Suntour Sprint stuff, but have the same problem.