Join Date: Apr 2009
Location: New Rochelle, NY
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
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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
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.
An ounce of diagnosis is worth a pound of cure.
“Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin
“One accurate measurement is worth a thousand expert opinions”
- Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance
Last edited by FBinNY; 08-03-12 at 01:58 PM.