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08-03-12, 01:24 PM
I want to sell my old mountain bike stem but don't know how to measure? i do have calipers.
There are a few dimensions.
The fit to the fork, ie the diameter of the quill, usually 22.2mm (7/8") or 1" to fit into the fork with threaded headsets, and 1-1/18" 1" (rare) ID, to fit over the fork in threadless versions.
The length (or extension) which is measured along the horizontal (or sloping) top from the center of the fork to the center of the stem. These are typically in 10mm increments, so you can use a ruler and eyeball the measurement. Note. there are a few stems that measure on the 5s but they're rare, and usually only toward the short range, ie, 85mm or 95mm,
Then there's the stem angle between the extension and line of the fork. You'll need a protractor, and a straight edge to measure this.
Here's a picture of stems (http://www.brightspoke.com/t/bike-stem-calculator.html) and the measurements.
Then if you have a quill stm, there's also the height. Some folks measure the overall height, others only from the minimum insertion line to the top. This is usually not discussed except when someone is shopping for a tall stem - non-standard.