Originally Posted by
repechage
I would change that to a believer of Jan Heine. Any of the steel thin walled tube of the same outside diameter are going to flex just a bit more than one of thicker wall thickness and given equal build attention and care. Going oversize in diameter with thin walls gets you a stiffer bike. But, even with the more modern heat treated steels, air hardened etc, the thin wall thickness may also make the bike a bit more "fragile", easier to dent locally, more likely to fold up in a big crash.
One could probably save more frame weight by carefully selecting a pressed bottom bracket shell, fork crown, dropouts and lugs than going silly thin on the tubes. Silly thin tubes and light fittings will of course get one the lightest frame yet.
Yes, I neglected to qualify my POV with teh caveat "with equal OD," since with early 753 and 531 SL, the ODs were teh same. In this situation, thinner wall would result in a less-stiff frame tube, and presumably a less-stiff frame. I never said anything about oversize tubes v. thin tubes, nor about other fragility factors such as tubing collapse aka beer-canning.