Stem swap??
 

I have a 100mm stem with a 105 degree rise. I want to swap to a 90mm stem to get a bit of a shorter reach, but would like to keep the same handlebar height. Does anyone know if I should buy a 90mm stem with a 115 degree rise or a 90mm stem with a 105 degree rise? It seems to me that a shorter length stem with the same degree rise will set the handlebar lower. Anyone know if this is right??

Is this a Trig question?

The bar height will be length * sin(rise angle - 90). If you keep the angle the same, and shorten the stem, the bars will get lower.

Yeah, I kind of asked the question in s stupid way. I knew it would lower the handlebar height a bit. Just couldn't visualize how much lower the bars would be. Found this reach/rise graph online, which helped me figure out what angle stem to get to keep the same bar height but shorten the reach: http://www.habcycles.com/fitting.html

Funny! Most people ask how to raise the stem height!

I think that should be length * sin(rise angle - head tube angle) - if the stem angle is equal to the head tube angle, then the stem is horizontal and the height wouldn't change, and if the stem angles downward from the head tube to the bars then shortening the stem would actually raise the bars.

Remember to put your calculator into degrees mode before you do this - if you're not sure, take the sin of 90; if it's zero (or very close to zero) then you're in degrees, otherwise you're likely in radians!

105 degree rise?

0 degree is completely flat. 45% is midway point. 90% is perpendicular, 105 degree is coming back at you.

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.