Originally Posted by
Campag4life
Sorry, you are being overly simplistic. It is more involved than that. Not hard by any stretch...but you don't know the interior angle you mention...it isn't the complement of the sta...as most bikes today don't have a horizontal top tube...have effective and actual top tube length. You need all the dimensions the OP mentioned plus BB drop.
OP...you can get a simple free 2D CAD software on line as well. Pretty easy to plot everything. Also if somebody posts the equations, I will check them with my Roubaix. I know all the dimensions on the bike including stack and reach.
Well that was my point about the measurement being actual and the assumption of top tube being horizontal in my first response. I know modern frames are seldom that, but knowing how the original measurements come from would determine if we need another piece of info.