Originally Posted by
bicyclebits
Kergin,
Look in the chainstays when you tear down the bottom bracket. A flashlight should show the welded seams if the stays are hi-tensile or you can feel them with your finger.
Infinity is, in fact, seamed tubing, even though double-butted and pretty high quality (IMO); so a welded seam would be found anywhere you look. The Nishiki I've mentioned has the seam clearly visible in the seat tube, though it's more visible than palpable. The steerer tube (Tange) doesn't appear to be seamed, FWIW.