Ok i been having this doubt for zillions of years and I need somebody to explain it to me ok?
This is the deal...
For example, steel frame with 73 degrees st angle, front tube 73 degrees also. Now, of you make an imaginary line (parallel to the ground and tt) between the rear and front dropouts, the intersection with the seat tube with this imaginary line has a different angle, not 73 degrees, lets say 72.8 or whatever... why is that??? Anybody knows the reason?
By geometry it should be the same angle, opposite angles between parallel lines, but looks like in bikes is not like that, anybody?