How stem length is measured

[quixoticgeek]

On a straight non angled stem, the length is pretty obvious. On angled stems, is the length the actual length of the stem, or the equivalent horizontal length? Or to put it another way, is it the Hypotenuse or the Adjacent?

Thanks

J

[Samuel D]

On the stems I’ve had, it’s been the actual length of the stem (hypotenuse). However, this has only been approximately true, suggesting there is no standard places to measure between. The stems have also varied in clamp height and where exactly the centre of the main tube intersects the clamp.

The saving grace is that handlebar position is a lot less critical than saddle position, so a few millimetres here or there doesn’t make a difference except in edge cases (the millimetre that broke the cyclist’s back!).

[Brucey]

I agree it is usually the length from the centre of one clamp to the centre of the other, i.e. 'hypotenuse' (although it isn't really a right-angled triangle because the steerer tube isn't vertical). This means that (with the same length stem) the forward reach reduces as the angle increases, in much the same way as it would with an angle-adjustable stem.

Retailers don't always know what the correct measurement method is, e.g. see contradictory Q&A answers here;

http://www.wiggle.co.uk/bbb-bhs-25-highrise-oversize-stem/

You may find this page useful

http://habcycles.com/fitting.html

cheers

[LittleWheelsandBig]

Most manufacturers measure stem length centre-to-centre along the top of the extension. Nitto measure centre-to-centre along the centre line of the extension, which gives a small difference in length.