Originally Posted by Cactus
DannoXYZ,
You're just so hostile - or is it just Macho? Anyway, given your superior engineering knowledge, why don't you show us the calculations and specification of your 2" twist. Without that, all your engineering talk is just spew.
Nothing about the picture shows where the flex is occuring. Look closely at the top tube, its moved. That the ends of the bars are in different positions proves nothing. It is true that a larger diameter stem will be stiffer, all else being equal. Rarely is all else equal, but that ignores the question of how much stiffness is necessary.
Sorry, I only get defensive when I report the facts and other people operate out of rationalizations and jumping to conclusions. I'll see that a bear killed a squirrel and ate it and I'll report just "what happened" . Other people will try to say why that's "bad", "good", "silly" or that it didn't happen at all; we're talking about two different things completely. I say that bar-end flexes 2" and that's indisputable (see picture below), yet you not having experienced it doesn't make it either "good" or "bad" or "silly" or "untrue".
You question the discussion of why? Why is what its all about. All the differences that you note for people to chose between, are all about why. Why should someone chose one over the other?
Debating "why" is like arguing why your preference of chocolate ice-cream is better than someone else's choice of rocky-road. Each person will have their own rational and subjective judgement, and they're all different. That's fine. Doesn't change the facts. Based upon each person's needs and requirements, they just select the attributes that work best for them. For some, styling and height-adjustibility is important, so quill-stems may best fit their needs. For others, stiffness and weight might be a factor and they can put up with some industrial-looking ugliness; that's fine too. Both choices are equally "good". There's no one "right" answer. Just because someone else chooses a different result than what you want (vanilla vs. strawberry ice-cream), doesn't make their choice any more or less superior or inferior to yours.
Lots of stem breakage at your shop, eh? Guess I'll avoid it. That's not common with well maintained bikes. Yes, some racers, on the edge, break parts of all kinds. They are generally exploring the engineering limits of the parts they use. Usually, its unncessary - like Hincapie's broken steerer. That is, a couple of extra ounces on a bike to make sure it doesn't break is not only good insurance, it won't hurt performance. No one that I have read has been able to extract, from real world performance, the benefits of having one of the lightest bikes in an given contest. Forget the theoretical calculations of energy to raise a gram a meter in elevation. Real world results don't mesh with the calculation.
It's already been shown that Hindcapie's failure was due to the stem-cap being cinched up INSIDE the stem itself rather than resting on top. This yielded insufficient clamping on the steerer which required additional tension from the pinch-bolt. This squeezed the parallel sides of the stem into a trapezoid with the tight spot on the bottom pinching the steerer, resulting in a concentrated pressure point and notch-failure. It had nothing to do with the design of threadless itself.
And designs are always improving. New techniques are tested and tried in the field, racers being probalby the most punishing on their equipment. Our shop was the biggest in town and supported all the local clubs, so yes, we'll see a lot of equipment failures from racers. The large data group from our shop also points out the differences in the designs with not a single threadless stem failing. A major contrast to the quill-stem failure rates. Rationalize "why" as you will, the data and facts don't change.
Eventually we'll cease to see quill-stems being produced at all, except as vintage and collectors items. It's like debating drum vs. disc brakes, many people were resistant to the advance and progress of technology. Porsche and Ferrari were one of the last ones to adopt them with all sorts of rationalizations on "why" they're not desirable. But the facts and data on disc-brake's superiority is beyond judgement and eventually they too, must accept the new advanced designs. Look at Edison vs. Westinghouse...
One other point, the ease of changing bars is another red herring. To change bars, one has to remove the brake levers/shifters, bar tape/pads/grips, & accessories regardless of the stem type. If the need to thread the denuded bar through a clamping stem slows down the change operation by any significant amount, then the mechanic isn't very good. IMHO
Sorry, I should've said "changing stems", which is required much more often than changing bars. Reach and height measurements will change as a rider progresses. Higher fitness and flexibility after the first couple of years will usually require a longer and lower stem.