Originally Posted by
Kontact
Supposing the same seat tube angle and same top tube length, a bike with a 73 HTA will have a front center or wheelbase about 1cm shorter than a bike with a 72 HTA. Both head tubes originate at the top, and angle down from the top, so the net effect is seen at the front dropouts.
Are you assuming fork offset will remain constant? There's no reason to do so, especially since we're in C&V where steel forks are the norm, rather than in the world of carbon, where forks only come in a very limited range of offsets. Put a 2 1/2" (63 mm) fork rake on that 73 degree head angle and the front center and wheelbase are going to be a lot longer (and trail a lot less) than if it had a 43mm.