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how do you measure stem length?

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how do you measure stem length?

Old 10-29-07, 07:16 PM
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Bolo Grubb
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how do you measure stem length?

Is it from the center of the fork clamp to the center of the bar clamp? Does the rise angle affect the length?

I am trying to update an older bike and bought a threaded fork adapter so I could use an old stem that I that I have. Turns out that old stem has a 1" fork clamp and the stem adapter has a 1 1/8" clamp area.

So I either need to get a new adapter or a new stem. But I am not sure what the length of the old stem is so not sure what to order for a new stem.
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Old 10-29-07, 07:21 PM
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center of the steer tube to the center of the handlebar
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Old 10-29-07, 08:14 PM
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Originally Posted by Ingleside View Post
center of the steer tube to the center of the handlebar
Yup.
http://www.cyclingnews.com/tech/fix/?id=roadposition
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Old 10-29-07, 08:17 PM
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thanks guys
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Old 10-29-07, 10:18 PM
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And for the second part of your question, the angle will affect the effective length of the stem (i.e. how far the bars are from you) but it will not affect the measurement.
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Old 10-30-07, 07:59 AM
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perfect. Thanks Sivat.
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Old 10-30-07, 08:58 AM
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Not to be picky, but the dimension from the stem longitudinal centerline to the center of the handlebar is called the stem extension, not length. The angle will affect the reach and the rise.

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Old 10-30-07, 10:50 AM
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That graph is very helpful to my understanding. Thank you very much.

Now I need to read up on how to do the actual mechanic work
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Old 10-30-07, 09:17 PM
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Originally Posted by Scooper View Post
Hey Scooper -

Is the QBP catalog from which this is clipped available online?

Thanks!
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Old 10-30-07, 09:56 PM
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Originally Posted by jwa View Post
Hey Scooper -

Is the QBP catalog from which this is clipped available online?

Thanks!
Sorry, I dunno. I scanned it from a hardcopy.
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Old 10-30-07, 11:43 PM
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Use some basic geometry to measure the effective length.

You can use: http://www.carbidedepot.com/formulas-trigright.asp

Angle A = (90 - HT angle) + stem rise [for example, for a standard 73-degree head tube, a 10-degree rise stem would be a 27, flipped over at a negative 10 degree rise it would be a 7]
Side C = stem extension

Calculate...Side b will be the effective length coming straight out from the steerer tube parallel to the ground.

I use this site to figure which stem I need to change the effective length and height of the handlebars with a new stem. If you run the geometries of two stems, you can see the difference in both reach (side b) and height (side a).

Last edited by JiveTurkey; 10-31-07 at 12:09 AM.
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