Originally Posted by
JohnDThompson
Yes, that's too nice a post to do irreversible damage.
Tange #2 has the same physical dimensions as Columbus SL, so the seat tube should be 27.2mm ID. It likely was distorted slightly during brazing. Reaming should be fine. I'd use an adjustable or helical reamer rather than a hone, as hones will remove material from the entire circumference of the tube, while a reamer will only take off the high spots.
That you can insert the post that far argues strongly for distortion of the tube; reaming is the proper fix.
Thank you for more excellent replies as always.
John, interestingly enough the Centurion ProTour came with a 27mm seatpost according to the original sales catalog. So I do believe the 27mm post is original
That said, this bike has clearly seen a LOT of miles if going by appearance alone and I wouldn't doubt if the seat tube is lightly deformed at the top section near the binder bolt, and I'm seeing more and more benefit to having it reamed professionally. More common post size, knowing the seat tube is now as true as possible, likely achieving a better seat post fit than it has stock, not modifying this lovely post...
OTOH it sounds like modifying the post isn't that crazy, less risk than damaging the frame (though I trust a frame builder to ream it correctly), that video made the clean up work look pretty easy
The right ream seems to be $140, I also wouldn't mind investing and practicing, I have tons of junk steel frames I could practice on...
I'm going to keep thinking on which route I'll take and update as things happen.