Originally Posted by Don Cook
It is absolutely clear from the pictures that the entire bike is being tilted as pressure is being applied to the handle bars. Just look at the angle of the head tube as the bars are being twisted. That being said, if you think threadless stems are better, great! If you're a thread & quill person, amen! I have both. I ride both. I've installed and adjusted both. There are a few ridiculously and objectively wrong statements being made in this thread about both systems. Why do we find comfort in conversion of others?
Yeah, I tried to keep the front-end as vertical as possible, but you can rotate the picture to make the headtube & steerer prefectly vertical if you want. The bar's angle relative to the steerer/headtube is still not 90-degrees, showing twist in the stem. Just measuring the distance between the left and right bar-ends to the fork-crown will take care of eliminating the small rocking of the entire bike or flexing of the wheels & fork:
The different distances only show movement between the bars and fork-crown. This is flex in the bars, stem and steerer-tube, anything further away is irrelevant in contributing to this distance. This difference in rigidity of the front-end doesn't make any difference in efficiency or speed, but it does give you better feel and control in sprints. I'm also a little leary of snapping stems and bars in sprints and the further you stay away from the material's yield and ultimate-strength limits, the better.
Originally Posted by OLDYELLR
How would that be? Not actually having had one apart, I'd assume you just push the stem clamp thingie down until it stops and tighten the allen screws, making sure the bars are straight. How precise is that? When I adjust my hubs after repacking, I turn the cone a fraction of a turn at a time to get the clearance exactly right. Same with the adjustable cup of my bottom bracket. It's a micrometer-like adjustment. A threadless headset seems agricultural in comparison.
Well, normal threaded steerer is 1x24tpi thread giving you 0.00012" vertical movement per degree of rotation. Threads on star-nut/stem-caps are usually M6x1mm giving you 0.00011" vertical movement per degree, slightly finer. In either case, you can adjust bearing-clearance as precisely as needed.
The vertical bearing-clearance adjustment on the threadless is also independent of the rotation angle. You adjust the bearing clearance so it's smooth without binding using the stem-cap screw. Then you adjust the stem's rotation by spinning the stem around the steerer (or the other way around, doesn't matter). Then lock it all down by tightening the pinch-bolt on the stem. This locks in the bearing-clearance as well as the rotation adustment. You can also adjust the stem's rotation to center the bars later if you need to without disturbing the bearinng clearance as well.
Here's a site showing the adjustment procedures for both threaded and threadless headsets:
ehow.com - How to Adjust a Bike's Headset.
Again, I'm not saying that one design is better or worse than the other, just that they have different characteristics and attributes. Depending upon your own personal desires, you can choose one or the other, doesn't matter to me. Notice that I use a quill stem on my bike...
