# Measuring stem length.



## Thinkly (Apr 9, 2007)

I've always thought that you measured a bike stem from center to center. Center of HB clamp to center of stem bolt. However when I measure the stem on my mountain bike that way with my calipers it reads right at 95 mm. What gives?

It says on the side of the stem 25 degree rise and 110mm.


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## Bikinfoolferlife (Feb 3, 2004)

Are you measuring the reach? You measure center to center, along the length of the stem itself...

ps here's a diagram https://www.habcycles.com/stemfit.jpg


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## Thinkly (Apr 9, 2007)

That is how i am measuring and it comes nowhere near 110mm.


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## Bikinfoolferlife (Feb 3, 2004)

Mismarked if you're doing it right. Curious, what brand/model is it?


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## Thinkly (Apr 9, 2007)

Bikinfoolferlife said:


> Mismarked if you're doing it right. Curious, what brand/model is it?


Bontrager Sport.


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## gmcttr (Oct 7, 2006)

Are you measuring the distance labeled "Extension" on the Habanero diagram? The "Reach" is NOT what you measure.


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## Thinkly (Apr 9, 2007)

gmcttr said:


> Are you measuring the distance labeled "Extension" on the Habanero diagram? The "Reach" is NOT what you measure.


I guess i am not smart enough to understand the chart. What i do know is my head angle is 71 degrees, the reach measures 88 mm from center to center. It is supposed to be a 25 degree rise stem and is marked 110mm.

How do i use that chart knowing the above? I have to admit ignorance. :blush:


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## Thinkly (Apr 9, 2007)

why does nashbar say to do it like this?










https://www.nashbar.com/tech/sizebike.cfm


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## pipes10 (Mar 11, 2007)

^^that is how a stem is measured...it seems u are measuring the reach as per the diagram which will give u less than the actual length of your stem...just look in the upper left corner...u will see how u measure the stem by looking at the "extension"...u don;t need the rest of the chart in this case


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## gmcttr (Oct 7, 2006)

A 90mm stem and a 100mm stem with the edges of the blue tape marking the center lines.


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## Margaritaman (Aug 25, 2008)

A lot like top tubes with actual length and effective length. The greater the angle of rise, the less the effective length will be, or reach in the case of a stem.


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## Thinkly (Apr 9, 2007)

Very good information. Good job! I appreciate it.


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## Bikinfoolferlife (Feb 3, 2004)

You got it now? In my first post I was asking if you got your figure of 95mm by measuring the reach instead of the length, then I specified how to measure the length of the stem. Nashbar was telling you the same thing as to measuring length. You kept measuring reach, thinking it was the length is all I can figure...or was it just understanding the difference between reach and length and it was margaritaman's analogy with the top tube that made that clearer? Just curious....


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## Thinkly (Apr 9, 2007)

Bikinfoolferlife said:


> You got it now? In my first post I was asking if you got your figure of 95mm by measuring the reach instead of the length, then I specified how to measure the length of the stem. Nashbar was telling you the same thing as to measuring length. You kept measuring reach, thinking it was the length is all I can figure...or was it just understanding the difference between reach and length and it was margaritaman's analogy with the top tube that made that clearer? Just curious....


I was measuring reach. Plain and simple. Can't really tell you why, i suppose it is just my public school education.  Honestly i was just putting my calipers just like theirs and that IS what it measures.

What i didn't account for was the severe rise in my stem. Or in other words i wasn't measuring from the side because the pic showed measuring from the top.










Mine is more like this one.


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## Bikinfoolferlife (Feb 3, 2004)

Nashbar's picture wouldn't work with your stem, as the calipers wouldn't be a good way to illustrate the measurement, probably why they used a low rise stem. Their written directions were clear, though. They closed F88 so just this comment: I went to public schools, glad I didn't go to a parochial school.


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## Curious-George (Aug 10, 2008)

thought of something cool using simple geometry, couldn't we just take the reach measurement and multiply is by the cost of the angle since we know that the stem forms a triangle?

so we could do reach*cos( in degrees) = stem length


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## gmcttr (Oct 7, 2006)

Curious-George said:


> thought of something cool using simple geometry, couldn't we just take the reach measurement and multiply is by the cost of the angle since we know that the stem forms a triangle?
> 
> so we could do reach*cos( in degrees) = stem length


Or just use the chart linked in post #2 to see all possibilities at once.


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## Curious-George (Aug 10, 2008)

ya but with a hefty calculator its all good


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