Originally Posted by
AzTallRider
Personally, I think that trying to make bikes with differing geometries match exactly is both futile and unlikely to produce the desired results (those being comfort and performance). The most common denominator is saddle height, but even that can vary a bit between two "perfect" setups. It's because what matters in fitting is dynamic, and many factors come into play as you pedal the bike. If you have greater bar drop, that might influence the saddle angle, which might influence the saddle height. Being a touch more stretched out may mean you need to be a touch higher... or lower. It all comes into play, and what matters is what happens when you are pedaling, not when you are in a static position. Different geometries will handle differently, and that may mean that you want to be further forward on one bike than another bike with different angles/wheelbase/fork/etc. You are seeing that when you expected to see the front axle in the same place and it wasn't. What matters is the handling and how you feel when riding the bike.
Proper fitting is a process, not a single event, and the 'perfect fit' changes with your fitness and goals, which may also differ from one bike to the next. IMO, you can't just peg the relationships that work on one bike, and apply them to another.
^^^This. I have setup so many bikes at first trying to make each identical by measurement but discovered each bike felt different anyway. Even if everything is transposed perfectly, the bike will feel unique based on its geometry and how you balance on it. Get each bike close then ride it to tweak the contact points so it rides and feels like you want it to. In the end, one bike might always feel better regardless and it is the bike that has the best combination of geometry and fit that suits you. That doesn't make the other bike unrideable, they will just never be as perfect as the "one".