Originally Posted by oldbobcat

So if the common wisdonm got tire (wheel) width wrong, how much other stuff did they miss? This has the makings of a conspiracy theory.

Look at it this way. If you move your hand 4 cm in either direction on a 40 cm handlebar, you rotate your steerer 11.45 degrees. If you do that on a 30 cm handlebar, your rotation is 15.27 degrees. That's assuming a 0 cm stem. Actually, the longer the stem, the smaller the rotation, which is one of the reasons people in this forum get hung up on stem length for stability. Anyway, it's been my experience that the closer your hands are the stem, the less leverage you have on the handlebar, which means your handlebar inputs will be less controlled, which means you'd better become more skilled at steering your bike using by shifting your weight. Which is what experienced time trialists become very expert at. But wait, you might say, mountain bikers are very good at steering by weight shifting, and they have wide handlebars. Why, yes, a mountain biker carving through a fast downhill corner steers mostly by shifting his weight, but he's using the leverage of his wide handlebars to fight the deflections on his front wheel caused by rocks, roots, ruts, sand, and mud. You'll also notice that a lot of time trialists will eschew the extensions while negotiating tricky corners.

There's also the leverage on the handlebar that's used to propel the bike forward. You'll notice that those expert time trialists move their hands off the extensions when they're sprinting from the starting line, sprinting out of a corner, or jamming up a hill. That's because they're using their backs arms, and shoulders. To demonstrate to yourself, try climbing out of the saddle with your hands on the top of the bar, close to the stem.