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Stem geometry(4 posts)

Stem geometryjaybird
Feb 6, 2003 9:58 AM
Ok, this may be just a dumb question, but could somebody clairify the the whole stem angle geometry thing. All I know is that I have a Look 381i with a 120mm deda newton stem. I think my stem has a -17* rise could that be right? If i put it one way it is paralel to the ground and If i turn it over I have a slight rise. The ht angle on my bike is 74*.

I am looking for a shorter stem 110 - 100 and I would like a little more rise if possible. It seems as though every manufacturer uses a different measurement for their stem. On the component board there is talk about 90* and 85* stems. what gives?

spank you mucho,
J.
Yes.Spunout
Feb 6, 2003 10:49 AM
You have a -17 now. Flip it over and you'll have +17. You might like it, the trig works out to shortening your reach anyways.

90* doesn't change much when you flip it over. Honest, try it!

85* stems go five degrees either way. Flip at will.
many variables....C-40
Feb 6, 2003 1:07 PM
If you truly have a 73 or -17 stem (they are the same). Then then it should have a very steep rise of 34 degrees from horizontal when flipped. It should raise the bars about 6.7cm (2-5/8 inch). The reach will be greatly reduced from 120mm to 99.5mm.

It's more common for a threadless stem to have an 80 or 84 degree angle, that can be flipped to 100 or 96 degrees, respectively. A flipped 80 will raise the bars about 3.5cm and a flipped 84 about 2cm. Both reduce the reach by about 1cm.
Stem calculatortarwheel
Feb 7, 2003 5:34 AM
Here is a good link for understanding stem geometry and picking the right size. It shows how stem reach shortens as you increase the rise and vice-versa.

http://www.habcycles.com/fitting.html