How to measure stem length?

[Blodwyn Pig]

 I quite fancy a new one piece polished stem
https://www.google.com/url?sa=i&source=images&cd=&ved=2ahUKEwj9xLGq-pjlAhVOXBoKHXx5D5sQjRx6BAgBEAQ&url=http%3A%2F%2Ffreshtripe.co.uk%2Fvelo-orange-tall-stack-threadless-stem%2F&psig=AOvVaw3G6z7et4fCbk1Tl7JHO3gn&ust=1571046474830410

But I cannot work out what length, either a 90mm or 100mm?  Or rather I cannot work out how to measure  / how manuf  measure their stems.

IMG_0982 by mark tilley, on Flickr

Here is my old stem, sold as a 100mm, but 0 deg rise,  but this was a tad long used with Nitto Noodles. Note it measure 100mm from the edge of the flange to c/c , NOT c/c to c/c.

IMG_0986 by mark tilley, on Flickr

Here is my current stem, also 100mm?, but flange to c/c is 90mm, but

IMG_0987 by mark tilley, on Flickr

C/C is  100mm ?     

what is the correct way to measure?

[LittleWheelsandBig]

Most manufacturers measure along the top surface of the stem centre-to-centre (as per last photo). Nitto measures c2c along the centreline of the stem, not the top surface (as per first photo).

https://velo-orange.blogspot.com/2018/01/stem-measurements.html?m=1

[Blodwyn Pig]

forgot to say, that when fitted, the Easton has a 10mm further reach from c/c to nose bolt.

[ACyclingRooster]

The correct way of measuring a stem length is along the top of the stem from the centre of the bar clamp to the centre of the steerer clamp.
If the stem is of a steep angle then the tape measure is held horizontal from the highest point sometimes referred to as the virtual measurement.

[Blodwyn Pig]

ok, so the easton stem, was prob a 110m, but sold as a 100mm. Prob go for the 100mm then.  If the new stem sits on the locking spacer, it will be 10mm higher, with a 15mm gap at the top (min insertion 15mm),  but if I drop it down to the headset, it'll be same as now.  (or add 5mm spacer etc)

[Blodwyn Pig]

IMGP2963 by mark tilley, on Flickr


After much googlefu, I unearthed this from the Velo Orange blog spot. All their stems are measured this way. Will have to see if it makes any practical difference, when I remeasure tomorrow.  Now I'm confused...

[Blodwyn Pig]

http://yojimg.net/bike/web_tools/stem.php


A truly most excellent site, hours of fun, comparing stem lengths, angles, and heights on a graph,  with instant readout of the differences.

So The 90mm -17 deg VO stem with 75mm stack height  I was thinking about,  ends up, ( compared to my extg 90mm -7 deg 40mm stack height + 25mm spacers  = 65mm stack height)  with 2mm less reach, but 6mm lower..and that won't do. So I might need a 90mm 0 deg stem.