I'm building my first wheel and have a H Plus & Sons Archetype rim and a Shimano Alfine 8-speed hub gear. Looking at the spoke calculations, I have the Shimano spec which indicates a Flange Diameter of 104.3 and an P.C.D of 92.6.

But on the web, I'm reading that 'flange diameter' and 'p.c.d.' are one and the same(e.g.: here).

So if I'm using spokelengthcalculator.com, what should I use in the left/right flange diameter?

  • 1
    – Noise
    Oct 15, 2022 at 21:35
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    consider having the hub in hand to measure before buying spokes. Your rim, hub and spokes are unlikely to be coming from the same supplier, no?
    – Noise
    Oct 15, 2022 at 21:37
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    i think your link uses misleading terminology
    – Noise
    Oct 15, 2022 at 21:38
  • Thanks @Noise, I’m presuming you mean the non-Shimano link is misleading…?
    – Todd
    Oct 16, 2022 at 6:37
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    oh yeah, the video link, i don't think he's right or at least he's muddying the waters for newcomers
    – Noise
    Oct 16, 2022 at 14:51

1 Answer 1


Shimano uses their PCD numbers to describe the circle that runs through the center of the spoke holes. This is the number that most written references about wheelbuilding call the flange diameter, and is the number that the classical spoke length formula (which most spoke calculation tools use) is built to take as its input. So the basic answer is use the PCD and ignore the other one.

The other number is the outside diameter of the flange. There is never a time this is pertinent to a hand or small production wheelbuilder. It's there so that producers with automated lines can know which hub loading machines are compatible with a given hub before making their orders. For example, whether you can use the little Holland Mechanics hub filling station, or if it needs the big one.

  • Great - thanks! Those videos what pro-builders fall asleep to? :)
    – Todd
    Oct 16, 2022 at 17:01
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    @Todd Possibly, though I can assure you that in real life there's not quite as much techno and soft lighting around those machines... until after 5pm... Oct 16, 2022 at 17:14

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