I've been lurking around absorbing information and have built a couple lugged and one fillet brazed frames at this point. I picked up a medium set of S3 tubing complete that I'm not ready to build with anytime soon, but have a question about the seat tube dimensions that I'm hoping a builder who has made some of those frames can answer. The butting is a little funny, due to the nature of this tubing. One end is .61 with a 32mm butt and one is .51 with a 136mm butt, if I'm reading the specs I can find correctly. Am I wrong to believe the .61 end is the post end? Seems like 32mm is a very short butt for the post end of things. Also, it doesn't come out to the standard 27.4 id for a 27.2 post, but I would think the .51 end with the longer butt is the end for the BB cut?
Thanks for the help,