Originally Posted by Cactus
DannoXYZ,
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.
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
A couple of points:
First, looking at the picture, it looks like the quill stem is indeed twisting, at least a little. I can see the bike tilting a little bit, but the bars are tilting a lot more.
Second, your point regarding changing the bars is only partially true. To change all the components from one bar to another you are correct, threadless doesn't save much time. If you are changing the stem and not the bars, threadless is a HUGE time savings. To change the stem on a normal quill, you have to unwrap one side of the bars and remove one of the brake levers, so you can unthread it from the stem. To change the stem on a normal threadless stem you simply remove 5-7 bolts (usually all take a 5 mm allen wrench) and remove the bars and stem. Installation is equally difficult. Threadless does give you the option of 'flipping' the stem to allow some adjustment, and if you plan ahead, spacers give you a lot more room for adjustment.
God bless!
Wayne J.