Originally Posted by
rohmen
As I understand it, you subtract your headtube angle from the degree of rise listed by the stem manufacturer to get the actual angle of the stem above horizontal. So, I have a 105 degree (advertised) stem and a 73.5 degree headtube, which means the actual angle of the stem is 31.5 degrees above horiz.
Got it.
I've done many of these stem swaps so I have this handy dandy chart bookmarked:
http://www.habcycles.com/fitting.html
In response to your earlier question, I would suggest that you try them both out. How you feel in the cockpit is such a personal (& subjective) choice. Is there a possibility that your LBS can let you return one of the two with a receipt?
I've actually ridden with a stem that initially felt good, but after 2-3 long rides I decided not to keep, which my LBS took back.