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I've never given much thought to this aspect of fit, although it is a valuable tool. What is a zero degree rise (what is the starting point in marking off degrees?) and how much rise from zero is a 7 degree stem (over 100 mm) with a 73 degree head tube angle?
 

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A zero degree stem is usually 90 degrees from the centerline of the steering tube, so the line of origin is perpendicular to the steering tube.

You will see stems listed as 84/96 or +or-6. Both are the same. I prefer the road bike designation of 84/96 because all you have to do is subtract the head tube angle if you want to know the angle relative to the ground. For example, and 84 (-6) stem would have an angle of 11 degrees with a 73 degree HTA.

A +7 degree stem would have a 24 degree angle with the ground. The rise is the sine of this angle times the length, or .407 x 100 = 40.7mm.
 

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AlexCad5 said:
I've never given much thought to this aspect of fit, although it is a valuable tool. What is a zero degree rise (what is the starting point in marking off degrees?) and how much rise from zero is a 7 degree stem (over 100 mm) with a 73 degree head tube angle?
While you can work the trig to figure these things out if you'd like, here's a chart that makes it easy.


source

So, a 7 deg (up) stem on a 73 deg headtube would yield 17+7 = 24, and at 10cm = just a hair over 4cm's of rise. Flipped down, it would be 17-7 = 10, which is a bit less than 2cm's rise.
 

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Don't forget to throw into the mix your stem spacers - wether you put all of them below your stem or some above (or cut the steerer).

Edit: I was using a 17 degree 90mm stem with 1cm of spacers above the stem. Then I switched to a 100mm, 7 degree rise with all my spacers under it. The 100 degree stem was waaaay more comfortable.
 
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