Stem Sizing/Geometry


Man or Moose!
When measuring stem length, for a non straight stem (angled) which length does the length measurement refer to?

From centre of clamp to centre of clamp directly along stem body or, centre of clamp to centre of clamp measured at a horizontal projection from the steerer?

Sorry if this sounds confusing, but anyone who recalls pythogoras should be able to get where im coming from here.

Basically if the length is measured along the stem body, this would be the hypotenuse, hence the reach would be a fraction of this length. So to buy a specific reach one would need to buy a stem that was over length (if measured along the stem body).

I need to buy a steeply angled stem to drop my tri bars to get a lower possition plus and am thinking of getting a slightly longer stem to get a little bit more angle between my torso and arms (they arent quite at 90 degree's to my torso atm). So I need to know how they are measured so I can do some fiddling with the numbers.


Über Member
I have a BBB 30 degree stem, it's 70mm size.

On mine, it's the centre to centre of the two tubes it clamps to. your hypotenuse

the "forward reach" is a lot less than 70mm, perhaps 50mm? I'm not at home to measure it for you

I got a useful raise and reduction in reach with it.

Not sure all brands work the same though.

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