How do I measure a handlebar stem?
 

Hello all,

I've been looking on the net and I know it's out there, but I keep running into pages like this. Which is not what I'm looking for. I basically just need some proper guidance on how to measure a handlebar stem properly. I have a good idea, it just would be nice to get reassured somewhere!

Any and all responses will be most helpful and very much appreciated. :)

center lines . one is the steerer center , the other the handlebar center.
length is the difference between the 2..

It's not clear from your post what characteristic of your stem that you want to measure.
First there are two general types:
-quill stems
and
-threadless AKA aheadset stems

For quills you can have:
-different quill diameters
-different height (or length of the part that gets inserted into the steerer)
-different handlebar clamp diameter
-different forward protrusion, sometimes called neck or length
-different angle between quill and neck

For a threadless stem you can have:
-different steerer tube diameters
-different handlebar clamp diameters
-different forward protrusion
-different angle between steerer tube and stem forward extension
-of less concern, but still there, threadless stems can have different amounts of build height, the amount of room they take up on the steerer tube. Replacing one stem with another may require a change in spacers to be able to set the preload.

The diameters are most easily measured using a vernier caliper. Particularly for older road bikes and some Schwinns, you do need to get the tenths of millimeters right.

Forward extension is measured center-to-center. Angle is a bit tricky, but there are drawing tools and workshop tools to be had for the job.

If you're asking from a bike fitting point-of-view, when your hands are on the hoods, your handlebars, your eyes and the front wheel hub should align (you should not be able to see the front wheel hub).

That rule-of-thumb is a useful starting point but is often violated to make individual riders comfortable.

Finding the right length stem and a comfortable height can take lots of miles and experimentation IMO. Even the best bike fitters can only get close sometimes. A good investment is one of the types where the length is adjustable or some bike shops have boxes of cheap stems exchanged from new bikes which you can get several lengths and try them out before buying a good stem (or you may be happy with the cheap one). Hard to quantify but you want to have a position where you don't feel too cramped or stretched out and no sore spots such as your back, shoulders, wrists, etc. The longer your ride the more obvious a poor fit will show itself. This is a great site for comparing stem angles with length and height when you change stems of different angles but want to keep the same reach. http://www.brightspoke.com/t/bike-stem-calculator.html

Boy I'm hardly getting any notices on subscribed threads. All I ever got was fietsbob's posting!

OK so anyways I'm trying to accurately measure my stem so I have a good starting point when I go out and find a "better" fitting stem. I have measured my current stem as the pics show,

http://bikeforums.net/attachment.php...hmentid=353328 http://bikeforums.net/attachment.php...hmentid=353329

At first this looks like there's a length of 130mm on the stem, but if I was to get directly over the ruler, it looks like this is a 140mm in length.

BTW, I'm just interested in measuring the length of what I have. Sorry I didn't make that clear. So is this a 130mm or a 140mm or?

Thanks Crankycrank, from what that site it looks like I have a 130mm stem? Also, I'm betting that the treadless stems come in cm increments?

I measure along the side of the stem from the edge of the handle bar the midpoint of the steerer tube and add the radius of the handlebar, It can be difficult to find the exact point to measure from but since stems usually come in 10mm increments you can round to the nearest 10mm to make up for measurement errors. Measuring from the center of the top cap is only accurate if your stem is +/- 0°.

You might also want to look over your stem closely since most mfrs. will have the length and angle in small print somewhere on the stem.

Yes. And, and at least a few cases it's inscribed inside where the bar clamps, so is visible only when the bar isn't installed

Yeah there was no writing anywhere after taking off the handlebar. I did manage doing a good measurement and I think this is accurate? I come up with this being a 13cm stem. Sorry for the lack of good definition on the stem.

http://bikeforums.net/attachment.php...hmentid=353435

I'd say you have an accurate measurement at 13cm.