Bicycle Mechanics - Wheel build question re hub measuring and spoke length...

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Grasschopper
07-18-07, 07:28 AM
Ok so I got mu hubs from the Miche group buy and I am getting ready to build my wheels. Hub specs I have seen online seem to match the numbers I get when I put the calipers on the hubs...but lets check them.

The one I really have a question about is the Flange dia...all of the sources I have seen say this hub is 60mm. When I measure the hub the OD of the flange is 69.5mm but the hole circle is 60mm. I assume spoke calcs want the spoke hole dia...correct?

All the other numbers are pretty simple. Front hub center to flange is 33mm on both sides. Rear hub non-drive side center to flange 45mm, drive side 30mm. Spoke holes are 2.5mm. mine are 32 spoke hubs.

So given the above and the use of IRD Aero (Niobium30) rims which have an ERD of 577mm the numbers I get are this for a 3 cross build front and rear:

Front spokes - 279.2mm (so 279mm) Rear non-drive side - 280.9mm (281mm) and drive side - 278.9mm (279mm)

So am I correct that I should have my LBS cut the front spokes to 279mm, and the rears to 281 and 279? These numbers came from Spocalc.

Thanks

Scooper
07-18-07, 08:07 AM
You're correct in assuming the hub flange diameter is from the center of a spoke hole to the center of the spoke hole directly across from it (between centers of opposite holes in the hub flange). Go to Damon Rinard's website (http://www.damonrinard.com/spocalc.htm) and scroll down the page to "How to Measure Hub and Rim Dimensions"...

I always round down to the nearest mm since spokes do stretch, and if a spoke is even a fraction of a mm too long, you are likely to run out of spoke thread before achieving proper tension.