Stem Sizing Frustrations

Discuss light weight issues concerning road bikes & parts.
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Valbrona
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Joined: Fri Oct 28, 2011 3:25 am
Location: United Kingdom of Great Britain and Northern Ireland

by Valbrona

So, why when a stem is marked with 100mm or whatever length it might be, does it actually measure 5mm more? Is this just a little trick of manufacturers/re-sellers intended to mess us cyclists around? Why is there no industry-wide convention on this matter for the benefit of us consumers? Why do consumers seemingly count for naff-all on matters of convention in the cycle industry?

How about a directory folks indicating how stems are measured, eg.

A Felt stem typically measures 5mm more than the stated length.

by Weenie


Twinning
Posts: 87
Joined: Wed Jun 06, 2012 6:18 pm

by Twinning

Solution: buy from your local bike shop where you can see the item first.


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wpccrunner
in the industry
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Location: North Carolina

by wpccrunner

the stated length would be if the stem had no angle to it. When you have a drop or rise, the hypotenuse is longer than the effective length. If you measure the other side of the stem you will probably get 95mm for a claimed 100mm stem. Simple geometry. Same kind of thing with effective vs. actual top tube lengths.

+1 on using the local shop.

mrfish
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Joined: Wed Mar 28, 2007 12:49 pm
Location: Near Horgen, Switzerland

by mrfish

Agreed.

I understood Syntace makes or used to make some sort of "stem ruler" which allows you to calculate x and y positions

And I thought that different manufacturers measure slightly differently, similar to c-c or o-o for bars.

But bottom line it doesn't matter so much, unless you believe it matters to have your stem to within less than 5mm of its ideal position. IMHO you dial this out with thicker bar tape, minutely shifting your levers, bending elbows 1 degree more etc.

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DMF
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Location: Sweden

by DMF

Who, in their right mind, would go for a thicker bar tape to compensate for a 5mm taller stem? That's just ludicrous. One of the things I like about cycling is that you can be as OCD as you like about the fit. And when it all matches up just right, it is just freakin' heavenly!

"Changing your bar tape............"

Also, when the fit actually is perfectly dialled, then 5mm is a big deal. Not that you couldn't adapt, but for the OCD of it I feel you shouldn't have to adapt to the bike, the bike adapts to you. This is the beauty of it.

Geoff
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Location: Canada

by Geoff

Yup, that's the way it is. The moral of the story is: 'measure twice, buy once'...

5 8 5
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Location: UK

by 5 8 5

Don't manufacturers measure stems in different ways? Either horizontally or along the stem axis?

3T measures horizontally with a plus/minus 3mm tolerance (aluminium) . I thinlk the high tolerance is due to the difficulty in manufacturing aluminium stems to an exact length.

Image

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Rick
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Joined: Sat Aug 29, 2009 4:30 pm

by Rick

I have never had a problem with stems being anything but what they have claimed.

But I have never had a Felt stem. Maybe it is just that one ?

And I have always just assumed that stem length was "center to center" along a line that intersects the fork tube's longitudinal axis and the bars' axis.

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DMF
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Location: Sweden

by DMF

I'd say that there are many stems that measure over the top, not along the center (height wise), of the stem, which with an angled stem ofcourse comes out longer than a center measurement. It seems quite common practice. With a -17 degree stem the difference would be huge.

Valbrona
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Location: United Kingdom of Great Britain and Northern Ireland

by Valbrona

wpccrunner wrote:the stated length would be if the stem had no angle to it. When you have a drop or rise, the hypotenuse is longer than the effective length. If you measure the other side of the stem you will probably get 95mm for a claimed 100mm stem. Simple geometry. Same kind of thing with effective vs. actual top tube lengths.


How many stems have you come across in that shop of yours, if you indeed run one?

I have in my left hand a 4ZA Cirrus stem. It is marked 100mm/7 degree angle, and it measures 100mm from c-c.

I have in my right hand a Felt Ultralite that is marked exactly the same as the stem in my left hand, ie. 100mm/7 degree angle, but it measures 105mm c-c.


And it's like that with plenty of other companies as well.

totoboa
Posts: 88
Joined: Thu Dec 13, 2012 4:24 am
Location: Sierra Foothills, California USA

by totoboa

Maybe they're just men and exaggerate about the length of their stem. :welcome:

by Weenie


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