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Spoke length

Old 09-14-14, 02:52 PM
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Lambert
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Spoke length

Anyone knows the rim thickness of Velocity Dyad 700c? It's not on their website, as far as I can tell.
I am trying to determine the spoke length I will need for a Velocity Dyad rim with SP PV-8 dynamo hub. Each spoke calculator I consult seems to differ from the next. Sapim's calculator (Spoke calculator | Sapim) requires the rim thickness...

Thanks in advance!
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Old 09-14-14, 06:52 PM
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You don't need the rim thickness, you need a proper measurement of the ERD which take rim thickness into account.

If you have the rims in hand, it behooves you to measure the ERD yourself. It is very simple. Just Google, "how to measure ERD" and you will get lots of help. Be sure to use a method that considers the depth to which you want the spokes to penetrate the nipples. Also be sure to consider the stretch you will experience in the spokes. A rough approximation is that straight gauge 2.0 mm spokes will stretch 1 mm at 120 kgf. Ultra-butted spokes like Revolutions, Lasers, and CX-Rays will stretch about 2.0 mm at the same tension. Lower tensions will give proportionally lower stretch. And be sure to take several ERD measurements around the circumference of the rim and average the data to give a final result. Also separately measure both rims. They are very possibly not the same.

If you were wanting to order rims and spokes at the same time, perhaps you should not. Get the rims, measure the ERD, then calculate your spoke lengths and order the spokes. A bit of a PITA, but worth the trouble.

Good luck.
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Old 09-15-14, 08:43 AM
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ERD is listed.

Velocity Wheels

And now I actually looked at sapim calculator... so that would be no help at all...
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Old 09-15-14, 09:38 AM
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Originally Posted by brad06ag View Post
ERD is listed.

Velocity Wheels

And now I actually looked at sapim calculator... so that would be no help at all...
Yes, ERD is listed, but self-confirnation is highly recommended by the experts who inhabit the Mechanics forum. As for using the Sapim calculator, that has no advantages over any other one. Use one that doesn't ask for unavailable information. Spoke length is spoke length. Brand is irrelevant.
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Old 12-15-14, 12:43 PM
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For me, there is a reason. The Sapim calculator seems to be the only one that calculates from the outside in, rather than the inside out.

If you will, it takes the distance from the EndNut to the flange, rather than the Center to flange distance only. If one is tinkering with changing the OLD of a hub to fit a different frame, this calculation from the outside in provides a much better understanding of how much additional stress is leveraged on or off of the NDS.

Still, to use it, one must enter a # into that field. SO, says someone, if the known/measured ERD of the rim is, say, 606, then enter, say, 603 into the ERD and 3 into the rim thickness. . . But that doesn't yield credible numbers.

Frankly, it feels like it is asking nipple length, but it may already have some factor against a simple use of that number.

SO, how does one best calculate the rim thickness of a given rim?

I want this approach to calculation, and would be very happy if another engine with this approach is available.

Thank you.
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Old 12-15-14, 12:47 PM
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This is the calculator link:

‪Go here, and select for a “rear wheel” as type.

‪https://www.sapim.be/spoke-calculator
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1963 Hetchins Mountain King (the gravel grinder)
1971 Gitane Tour de France (The War Horse) (1 owner)
* 1971 Gitane Super Corsa (The Garage Queen) (crashed out)
1971 Gitane Super Corsa #2 (sweet replacement frame)
1980 Ritchey Touring (The Grail Bike)
1984 Tom Ritchey Team Competition (NOS show bike)
(replacing the stolen 1981 Tom Ritchey Everest custom)
1985 ALAN Record (Glued & Screwed. A gift.)

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