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How to calc spoke lengths for wheel build

dhobiwallahdhobiwallah Posts: 272
edited September 2012 in MTB workshop & tech
Having a bit of trouble working out what spokes to buy to have a first crack at a wheel build.

I have a Shimano HB-M555 rescued from a wheel I Taco'd last year and an old non-disc XC wheel that I would like to re-use the Mavic 217 rims from (because I'm Pikey before everyone asks).

Only prob is I'm getting confused trying to use online calculators - not least because the hubs don't have the simple 'pie dish full of holes' type flange on either side.

Random hungarian website - but has a picture!
http://ebike.hu/termekek/kerek/agy-elso/disc/7505+shimano+deore01+hbm555/

From shimano tech docs the hub specs are:

MODEL # HB-M555*
WEIGHT 236g
FLANGE DIAMETER 37.8mm(L) 44.2mm(R)
SIS COMPATIBILITY
OVER LOCK NUT DIMENSION 100mm
CENTER TO FLANGE (L) 33.5mm
CENTER TO FLANGE (R) 25.7mm

* On large flange side, subtract 1.5mm from spoke length. On small flange side, add 1.5mm to spoke length.

Specs for the rim I have found are:

Mavic 217 (ERD is Mavic's Nipple Seat Dia + 3mm for nipples) (26" MTB)

Effective rim diameter (ERD) 539.0 mm
Offset spoke bed (OSB) 0.0 mm

Can anyone help me work out what length spokes (and nipples) I need?

Using the sitehttp://www.wheelpro.co.uk/spokecalc/

And inputting the 'ERD' as the 'rim dimension' (ignoring the 3mm mentioned)

the basic length for a 3x came out at 263.5 - I'm guessing I need 16 spokes at 265 and 16 spokes at 262 :?: What length nipples should I get?

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