Mind boggling spoke length needs input

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Mind boggling spoke length needs input
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flag coolorochi
Posted: Nov 24, 2015 at 23:39 Quote
CRC build wheel:

Hope Pro II EVO SS/Trial hub
+ DT champion 2.0 spoke + 14mm nipple
+ spank tweet evo 28 rim

dt swiss spoke calculator give me : Left 235 Right: 236
other calculator give me : Left 254.6 Right: 254.9
3rd calculator give me : Left 256.4 Right: 256.7
measured old spoke: Left 255 Right: 256
local shop mechanic tells me : 267 for both

there are more than 3cm difference , how do I take it?
why is DT's calculator so short?

what should I buy??
flag RunsWithScissors
Posted: Nov 26, 2015 at 7:03 Quote
Based on what you've posted... If you are using the same hub and your new rim has the same ERD as the old one I'd just get 256 and call it good. You'll be 1mm longer than necessary on one side, but that isn't a problem with a double wall rim. If the new rim has a different ERD than the old one you just add or subtract half the difference between the two ERD's and move on. For example, if your old rim had an ERD of say, 548mm, and your new rim had an ERD of 552, you would need to add 2mm to your spoke length.

A quick look at the spoke calculator on Prowheelbuilder.com indicates that there are multiple models of the hub you're describing, including boost versions, so the discrepancy could be due to wrong hub dimensions. Also, you made no mention of number of crosses or number of spokes. FWIW, by making my best GUESSES as to what you have, the calculator says 255.1/256.7, which at the end of the day means 256 will probably work (again, assuming that the dimensions in the database are correct).

It all comes down to the quality of the input data. Bullshit data=bullshit results. Spoke calculators are all over the place and in my experience they all work as long as you use good input data. When my boss f*cks this up it's usually because he's relying on bullshit dimensions out of a database instead of actually taking the time to measure the parts himself or he's not paying attention to the number of crosses.

FWIW, the spoke calculator I like best is found at https://leonard.io/edd/ The databases aren't very complete, but the math is perfect. Buy a cheap set of calipers that read in mm, do your own measuring (correctly), and you'll never have a wrong answer again. It's not rocket surgery...
flag IMAKETHINGS
Posted: Nov 28, 2015 at 13:27 Quote
DT's calc is so short because you probably have 32 in the spoke hole diameter column. Go back to DT and check very carefully...Ø-SPOKE HOLE should be 2-2.5 mm.

I googled the dimensions on both the hub and rim and plugged them into DT and got 254.5 left side 254.8 right side accurate. I would go 255 all around based on that, but I'm just some guy on the inter webs so make sure to double check everything before purchasing.
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