umd

I got my -17D ARX team stem today; what I had meant order in the first place. The first thing I noticed when I unpacked it was that it seemed longer. Both are stamped with 100mm, but I measured it at 110 across the top. Are stems measured across the top, or in the horizontal plane? As you can see from the picture, they are both about the same length horizontally.

dmotoguy

"Length is measured along the stem from the center of the quill or steerer tube to the center of the handlebar clamp."



hhmmmmmmmm

Tapeworm21

It's kind of an illusion. Measure from the center of the clamp side to the middle of the handlebar. Then, put the stem on the rise so we can all laugh at you.

I'll agree though, it looks longer.

DannoXYZ 

Centre-to-centre of both circles. One of them might actually be longer. I've gotten mistaken packaging before. I've even seen stems stamped with the incorrect length on them.

Jynx

Its center to center but wouldnt the 17* appear shorter and not longer?

Coyote2

Just eyeballing it, that appears like it could be a 1cm difference. Might be mismarked.

And I agree with Jynx's comment.

bdcheung

Here's a spreadsheet that will help you figure out all things stem related:
https://home.gwu.edu/~bdcheung/stemcalculator.xls

Here's a website that does the same, but with fewer significant figures:
https://alex.phred.org/stemchart/Default.aspx

waterrockets 

Yeah, I think those stems are different lengths.

I've drawn some lines that should represent the axial center of the stem and the crossing points inside each clamp. My lines are obviously not centered with the near faces, but I think they're pretty close to the middle plane of the stem given the camera perspective.

If you want to look at this photographically, take the image from a lot further away, without zoom. This will eliminate much of the perspective. If your camera is high enough resolution, then the detail will be fine w/out zoom. Do you think you can find somebody with a sweet camera?

You can just tape-measure these on your screen to see that there's a big difference in the two lines.

DaveSSS 

The modern standard requires the stem to be measured at the side, at the centerline of the extension, from the center of the steerer to the center of the bar clamp. They are not supposed to measured at the top.

A 73 degree stem will be a couple of millimeters longer, horizontally, than an 80-84 degree stem.

It's easiest to measure from the centerline of the steerer clamp to the edge of the hole for the bars, then add 13mm or 16mm for an oversize bar. I just measured a Ritchey 4-axis 73 degree x 110mm stem an it's right on the money. 94mm + 16mm = 110mm.

Nate552

+1. Can you take your new 100 stem to a LBS and try to compare it to theirs? Maybe find someone else with a 100 stem with the same angle (different brand) and see if it's really mis-stamped or not?

bdcheung

The stem was probably stamped wrong - it definitely looks longer

classic1

At one stage different manufacturers measured differently. Some would measure across the top, others along the side. For example, I have 135mm ITM quill stems that measure 137 or 138mm across the top because ITM would determine the length measurement along the side. Cinelli and 3T used to measure their quills along the top, centre of clamp to centre of the bolt. I knew the measurements were off and it used to annoy the life out of me. My father had the same frustration with early versions of ITM and 3T threadless stems. Eventually UK mag cycling weekly explained it all in a tech column.

None of this helps you though because farked if I know how they do it now.

umd

I still can't decide if it's an illusion, a different size (stamped wrong), or just measured differently. Measuring through the centerline instead of the top per Dave's suggestion still puts the new one a half cm or so longer, but measuring along the bottom puts them at the same length. I guess since the top and bottom are interchangeable...

Anyway, I'll ride with it today and see how it is... maybe I won't care.

waterrockets 

Yeah, you can measure these any way you want, but they aren't the same length. I've rotated them to match the 73.5 ° Tarmac head tube angle, and I slid the top one out so it's directly above the other.

DaveSSS 

This isn't that tough. Measure from the green line representing the center of the steerer to the edge of the bar clamp hole, along the center of the extension. Compare the two. Once on the bike the 73 degree stem will be another couple of millimeters longer, horizontally.

With Ritchey stems, the 84 and 74 degree models will measure the same.

waterrockets 

Yeah, that's one thing to note, if you want to drop your bars, you'll get a longer reach if you don't shorten the stem at the same time (see spreadsheets above). On the other hand, these stems don't appear to measure the same length anyway.

waterrockets 

Lastly, the longer stem is clear here, where I've cut the bottom one off and laid it over the top:

Flatballer

Jeez. 3T has been giving you some trouble umd. First they mismark the angle on the package, now they mismarked the length on the actual stem.

umd

Yeah, no kidding. The length measured as DaveSSS suggested is longer than 100mm but shorter than 110mm, so I think they are just measuring differently rather than mismarked it. I.e. they think it is 100mm. However, I just rode with it for a little over an hour and I am satisfied with the position it is putting me in so far. I will ride with it for a while and see how it goes. I'm doing some climbing later today so that will be the real test, to make sure it's not too far away in a more upright/open position.

wrobertdavis

Yeah, how it fits is all that counts. FYI, the specialized technical drawings of their stems show the length is identical - just the angle changes. But the Italians always do it their way, which may not have any relationship.

Bob

Coyote2

waterrockets has some mad computer skills.

coldass

Do 3T measure by reach from the centre of the steer tube? This would explain your difference. Is this 110mm?

I have the same stem (-6x110), it is very nice for the money (Ergonova bars as well - tip - pick one size up for these). I feel it looks short for a 110...

umd

I'm not sure how 3T measures, and therein lies the problem. It is, or is supposed to be, a 100mm stem. I have Ergosum team bars in 40cm.

waterrockets 

The Gimp

Erik B

Autocad says based on your photo:
If the top stem is 100mm long center of steerer to center of bar
The lower stem is roughly 3.8mm longer. Viewed from above the bars are moved an additional 3.8 millimeters away from the steerer tube, not just down.

This of course is based on my ability to accurately pick the centers from the original photo.