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Stem geometry(3 posts)

Stem geometryjaybird
Feb 6, 2003 10:19 AM
I meant to post this here but I ended up posting it on the components section as well.

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,
re: Stem geometryHorace Greeley
Feb 6, 2003 11:19 AM
Deda Newton Stem has a posted (per website) angle of 82 degrees (other sites indicate 80 degrees). This translates into a positive rise of 8 degrees (82 stem - 74 head tube) or 6 degrees, depending on which published measurement you agree with. A -17 would be parallel with the ground if you had a 73 degree headtube (73 and 17 - 90 degrees). Depending on whether you have any spacers, your reach is effectively shortened the higher the stack.
re: Stem geometryNessism
Feb 6, 2003 7:12 PM
There is no set convention on how to denote stem angles. A stem that is parallel with the ground is sometimes called 73 degrees and sometimes -17 degrees. Using this same system, a 90 degree stem is the same as 0 degrees.

One thing to keep in mind is that as a stem above horizontal, it brings the bars back toward the rider. For example, if a 110 mm -17 degree stem is flipped over the reach relative to the horizontal will be reduced to about 94 mm. The key words here are "reach relative to horizontal".

Good luck.