Originally Posted by chaadster

Color me daft, but what is the nature of this 'axle/butt' problem? What's the dynamic? I've never thought of it in a meaningful way, or as an important measure.

Based on my own experience, shorter wheelbases 'buck' a little more over big bumps than longer wheelbases, but in terms of negative impact on performance, I don't have any associations there, aside from feeling shorter wheelbases feel more sporty.

And this from a guy who rides a mini-velo and a folding bike, where my butt is not only way out over the axle, but the whole wheel!