Originally Posted by
ColinL
if you measured effective top tube on both bikes you would have some idea about how much longer stem you'll need on the smaller one. but I can tell you that if you're already riding a 120+mm stem on your current bike it's very unlikely that smaller one is going to work.
Both bikes have horizontal top tubes. So, effective top tube = measured top tube. I have a 110 mm stem, which is mounted at the top of the steerer tube, and spacers below the stem effectively subtract about 40 mm from the horizontal distance between the saddle and the handlebars.