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Discussion Starter · #1 ·
Hopefully these aren't dumb questions...

How are stems sized? If a stem is listed as 90mm (e.g.), does that mean only that it is 90mm from top to bottom, or does it mean that the horizontal/x-axis length (when mounted) is 90mm (and that the actual physical length of the stem is greater than 90mm; assuming an angle on the stem, of course)?

I ask because I have a 90mm 17deg stem on my bike now, but would like the bars to be just a touch lower. I was thinking about going to a 90mm 6deg stem, but I am concerned that the change will stretch me across the bike more than I want to be. By my calculations, if stems are measured from top to bottm, a 90mm 6deg stem would result in 3.5mm more in reach (and about 15mm in drop) as compared to a 90mm 17deg stem. Is 3.5mm a negligible difference? Or is it something that I'm just going to have to try and feel out on my own?

Thoughts?

-face
 

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Length means just that, the length of the stem. That chart is very easy to understand.
Reach is a term commonly associated with handlebars.
 

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Springscylist
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Flip Flop

If your bike is fairly new you should be able to flip the stem over and get less or no rise. This is something you can try and see how it feels and go from there.
 

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nothing
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The length of the stem is determined by measuring from the center of the steering tube to the center of the handlebars. This measurement is represented by the reach measurement on the chart.
 

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wrong....

The length of modern angled stem is the extension dimension. The reach dimension was valid only in the days of quill stems, when all wre horizontal.

The poster need to consider that a +17 stem is much shorter in reach than the advertised length. He also needs to consider that fact the lowering the stem has a simiar effect to lengthening the stem. He's worrying about a minor length change, when the change in drop is far more important.

To answer the poster's question, a 96 (+6)degree stem will lower the bars about 33mm and lenghten the reach by about 14mm. It's a huge change.
 

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Here are some numbers..

from an excel spreadsheet somene sent me a while back:

INPUT: Stem Length (mm): 90mm 90mm
INPUT: Stem Rise (deg): 17° -6°
Combined angle: 36° 13°

Horizontal Reach 2.87" (73 mm) 3.45" (88 mm)
Vertical Rise 2.08" (53 mm) 0.8" (20 mm)
 
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