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  • Reaming should really only be for getting rid of lumps, bumps and distortion from brazing or welding, not changing the internal diameter of the tubing. Reaming that tube back to 31.7mm at any point would be fine. Trying to ream it out further to fit a bigger seat post is asking for trouble though.

    On Brommers Bike no. 3 I used a 31.7mm external seat tube, because that fitted the lugs I was using. I bonded a 30.6>27.2mm shim in place to allow me to use a 27.2mm seat post.

  • Aha, I had gotten to the understanding that the tubes warp during welding / brazing and are therefore sold with an ID slightly smaller than the intended seat post. And I got my logic backwards with the Zona tube, seems to fit the bill. Thanks!

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