Originally Posted by
chas58
I'm an engineer, but I'm not speaking theoretically. I'm speaking from my experience.
That example is moving from a 100mm stem to a 60mm stem on a road bike). 20mm change isn't a big deal, but 40mm sure is. Doesn't make the bike unrideable, but does keep me on my toes and require me to pay a little more attention.
If you're an engineer, maybe you know how to draw a free body diagram. What that will tell you is that there is no difference in moment when you shorten the stem. I went through this when someone asked me to make a zero length stem. I thought it was a bad idea and drew an FBD. You have to get to a fairly large steering angle (i.e., you would never get to this angle while riding at speed) before there is a difference between a long stem and no stem.