Re: [CR]Stem length vs. steering

I hesitate to go into off-topic territory with a science discussion, but if I restore bikes with different frame sizes, what should I expect in the way of handling when I adjust, say, a too-small frame with a long stem? I consider the upper body's mass as being foreward of, and pivoted at, the saddle, so any lateral inertial forces as during transient steering adjustments impart a lateral force to the bars, ahead of the steering axis. This is much more pronounced at higher speeds, and tends to counter the steering input that created it, i.e. steering into a turn tends to push the steering out, at least during more transient motions vs steady cornering. This distance ahead of the steering axis changes dramatically with even a few cm difference in the reach of the stem+bar, and this also depends quite heavily on the grip position used. For high-speed cornering precision and stability, i.e. not careening spastically through high-speed sweepers, I favor a longer stem with shorter top-tube. Of course the other frame geometry differences also contribute their own effects, making any changes in stem length relative to that geometry only, so different model bikes may prefer different top-tube/stem length ratios, for a given rider. For pacelining I like a shorter front-half wheelbase to allow closer drafting. A tight headset especially ruins the handling of any bike, btw. For climbing out of the saddle, a bigger frame and shorter stem usually works better for me. I ride a wide variety of frame sizes on a pretty regular basis, from 48 to 61cm, all fitted, with a maximum of 120mm stem (combined with a 55cm TT on my 48cm Mariushi and also 55cm TT on my Windsor). My larger Viscount and Specialized bikes with 57cm TT use 100mm stems. None handle poorly, but drafting on the big bikes takes more care to avoid touching wheels. My 56cm Masi with a 110mm stem just happens to corner with a particular ease and precision.

David Snyder
Auburn, CA