Bicycle Mechanics - Stem Diameter Measuring

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smovlov
01-29-09, 07:08 PM
What is the best way to tell what size bar a stem will take? I'm finding it very difficult to get an accurate measurement.
Panthers007
01-29-09, 07:12 PM
Either by measuring the handlebars that it had. Or by measuring them with a caliper. If it's a new stem, read the specs on it from the packing or an advertisement. You can also look on the internet for information.
Retro Grouch
01-29-09, 07:13 PM
Should be easy.
Take any handlebar and try to fit it in the stem. Notice if it fits loosely or if it looks like the handlebar is too big. Measure the handlebar. There's only a few choices so the answer will be obvious.
Road Fan
01-30-09, 04:53 AM
+1 to what Panthers and Retro said. Also keep in mind that it should not be easy to force a too-big (26.0 or 26.4 mm) handlebar into a smaller stem (25.4 mm).
You should be measuring with a caliper (check out Harbor Freight). You either need one that will indicate 10ths of a millimeter or one that will indicate 1000's of an inch. In the latter case you also need to be able to convert from inches to millimeters or vice versa.
Road Fan
HillRider
01-30-09, 06:10 AM
Some stems make it easy by engraving the required bar diameter on the quill or inside the face plate.
ldmataya
01-30-09, 06:57 AM
Sometimes it is hard to get a road shape bar through a stem, especially if putting a 26.4 in a 25.4, etc. For that reason, I keep short straight sections of bars that I've cut out of old and worn bars for this purpose. So I have 10cm sections of 26.0, 26.4, 31.8. Also works well for figuring out if some old mounting clamp is going to fit without scratching up a nice bar.
HillRider
01-30-09, 09:12 AM
Sometimes it is hard to get a road shape bar through a stem, especially if putting a 26.4 in a 25.4, etc. For that reason, I keep short straight sections of bars that I've cut out of old and worn bars for this purpose. So I have 10cm sections of 26.0, 26.4, 31.8. Also works well for figuring out if some old mounting clamp is going to fit without scratching up a nice bar.
I assumed 31.8 mm stems/bars are so obviously much larger than any of the others there is no ambiguity with them. The ones that are tricky to sort out are 25.4, 26.0 and 26.4.
smovlov
01-30-09, 05:24 PM
Anyone ever heard of a bar with a 25mm diameter? From what I can tell its Guidons Philippe stamped on one side and ATAX Professonnel on the other.
EDIT: Just did some digging, It appears it should be 26mm by this seller. (http://cgi.ebay.fr/cintre-course-alu-ATAX-professionnel_W0QQitemZ280303853464QQcmdZViewItemQQimsxZ20090119?IMSfp=TL090119127001r24693) I don't know why mine would be 25 but oh well.
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