Originally Posted by
gsa103
Tiller effect is slightly different than what you're describing. The tiller effect is due the bars rotating around the fork axis, not the center axis of the bars. As the stem gets longer, your hands don't move in a circle.
The MTB community is increasingly going to very wide bars with the shortest possible stem to provide stability at both high and low speed.
Longer stems are generally better for stability, but narrow bars and weight forward are much worse. That's why TT bikes are notoriously twitchy. Small left/right weight shifts cause steering inputs, with a wider bar, those are decoupled.
The handling characteristics are still based on geometry of the bike. From my experience...Transition Scout and Specialized SJ. Same bar width, same stem. The Scout is very twitch and easily put off line by rocks and roots...at my climbing speed. The SJ is much easier to control and I don't over compensate as I'm clumsily bouncing off of every rock within reach. Same on slower technical descents. The Scout seems to come into it's own as the speed goes up but the SJ is still more comfortable for me to ride. The Scout is a longer travel bike and intended to be ridden hard, I guess. But seeing as the bar and stem are the same it's got to be the geometry of the bikes, and maybe a little bit the wheel size difference?