Originally Posted by
Sy Reene
Ok, but you have HT and ST angles and fork rake. HT and ST angles are dependent on bike being horizontal. If you adjust the horizontal line, then the HT and ST angles would change and move away from the published values, right?
Anyway.. I was working with eg. a Geo chart that looks like the below. Just thinking there's a way to determine the theoretical Stack and Reach with all these numbers, a ruler, some math and a protractor :-) That linked calculator comes really close.
HT and ST angle give you a horizontal line, but there are infinitely many horizontal lines. The one that matters is given by BB drop, which not all geometry tables give you.
As I said, the guy who devised the system agreed that frame stack and reach depends on the fork (there used to be a lively aftermarket for both road and MTB forks, which is why I posed this question to him).