Carsten, could you explain something for me please? Everybody agrees that Klein frames were both very light and very stiff. Normally light and stiff is an either/or, not a both, so how did they achieve that?
Although the tubes were fat for their day, they weren't fat by today's standards and if the tube gauges were as thin as stated above then they were much thinner than today's, so how come the frames were so stiff?
gary wanted them to be stiff in the bottom bracket and head tube to achieve drive train and steering efficiency. the frames are not overly stiff in general. they are just not "noodely" like the typical steel or Ti frame. an aluminum frame shouldn't flex anyways for it to last.
also the MC1 era frames (until 1993) were not particularly light. Mountainklein, Pinnacle, Rascal, MC1 Attitude frames weigh 2000grams and more iirc. i think my medium MountainKlein frame with bottom bracket was 2300grams. Pinnacle and Rascal are not much lighter. only the MC1 Adroit frame is lighter with the thinner walled tubes and carbon/boron reinforcements. even back then there were lighter steel and Ti frames but they were much less "stiff".
a big step ahead in terms of weight were the Gradient tubes on the MC2 era bikes. the Pulse frame weighs 1500grams, 400-500 grams less than the Rascal which it kinda replaced. and even that is not overly light compared to current frames.
somewhere i have seen the wall thicknesses listed and they are far far away from a coke can.
that's just another half-knowledge over-simplification so typical for this board these days.
I assumed the coke can reference was just a figure of speech, obviously it's nowhere near the truth. Even with modern Scandium, which is a bit stronger than 7005, a XC downtube might be a 50 x 1.5/0.8/1.3, whereas even an Easton Ultralite 7005 DT might be 50 x 1.9/0.85/1.3. The same comparison (not a Klein) for the top tube is 38 x 1.5/0.65/1.2 (Scandium) and 38 x 1.4/0.8/1.3 (Ultralite). So the tubes available to Gary Klein must have been if anything fatter-gauge than the Ultralite and anything up to twice as thick gauge as an equivalent heat-treated steel tube.
I guess though that once a tube like a 50 fails, it can crush up quite a bit because the strength is all in the undeformed shape. It's a bit like an egg - once you've broken it, it loses all its strength, but until it's broken its shape gives it amazing strength in relation to the fundamental strength of the material.
Experience does seem to differ a huge amount - as is said above, some people would rate Pace frames as being as tough as they come, others have broken them. My own suspicion is that a lot of non-crash breakages are actually caused by an earlier crash that the frame appeared to have survived at the time but which caused the beginning of a terminal weakness.
From what you say, Klein frames clearly weren't 'crazy-light', but any frame will break in certain circumstances.