Originally Posted by Iowegian

Perhaps. The analogy of a spring was probably a poor example but as you mentioned, a bike frame constantly flexes and thus acts as a sort of spring. My point was that steel can sustain virtually infinite flex cycles as long as the material isn't pushed past its yield point. Whether the bike in question is compromised in such a way as to be dangerous I can't tell. The subject is way too complicated for me to fully comprehend and without knowing the alloy composition of the metal, the temperature the tube reached during brazing, the thickness of the tube wall where bulged vs the taper of the butting, whether the tubing was drawn or seamed, etc, it's all guess work. If I liked the bike, I'd continue to ride it, but that's just me.