Dt SpokeCalc and Wheelpro spokecalc giving different results

[stubob]

I'm looking at building some wheels this winter, and I'm trying to figure out spoke lengths. Using BHS's recommened calculator http://www.wheelpro.co.uk/spokecalc/, I'm getting different numbers than at Dt Swiss. http://spokes-calculator.dtswiss.com/Calculator.aspx

I'm planning on using BHS hubs, 71w front and 190 rear, laced to 50mm carbon/aluminum clinchers. Here's the relevant numbers:
Front PCD 31mm, center-to-flange 40mm
Rear DS PCD 49.6mm, center-to-flange 16.9mm, NDS PCD 38.5mm center-to-flange 37.6mm
Rim ERD 539.4

DT Swiss is saying 247 front radial , 244/246 rear 1x/2x, wheelpro is saying 256 front radial, 255/257 rear 1x/2x.

Somebody's either too short or too long, which is it?

[Mackers]

You typed 25 instead of 2.5 or whatever spoke hole size Bitex uses into the spoke hole diameter variable for the DT Swiss calculator.

[bikerjulio]

Wheelpro is correct for a 20 spoke radial front.

DT Swiss also makes a correction for nipple lengths, which I later found out only applies to their own brand. Other brands threading is in the same place regardless of length.

You forgot to mention the number of spokes.

Also I'd be doing 2X both sides at back. Don't see any benefit to a 1X NDS.

[Mackers]

I think he's planning 1xDS (heads in) or the spoke lengths don't make sense.
1xDS has resulted in broken flanges on these hubs though.

[bikerjulio]

Agree. hence my advice to go 2X both sides at the rear.

[stubob]

Looks like the spoke hole diameter was the problem. Don't know why I read that wrong, but I put the number of spokes in there, not diameter. Getting that set right got the numbers to match up. I had a feeling DT was making changes for nipple length, I had noticed small changes when changing nipple length. Measure twice, buy once...

I'm planning 20 front, 24 rear. Thanks for the advice on the 2x NDS, are the hubs ok for radial front?

[stubob]

Oh, and the reason I was shooting for 1x NDS lacing was based on this whitepaper from Williams that showed the relative tensions of various lacing techniques. I was hoping to get some of the NDS tension relative to radial (for balance), without as much tension change as radial (for longevity). 2x/1x seemed like a decent compromise, but if it's not going to make much difference, I'll stick with 2x/2x.

[bikerjulio]

BHS hubs are fine for radial spoking in front.

There is no consensus as to whether heads in or out is best, so entirely up to you. There was a discussion very recently on this.

Just to expand on the DT Swiss calculator and nipple lengths.

Before I knew any better, I'd assumed that a longer nipple would mean a shorter spoke. Because that's what their calculator does. Really quite misleading. For any other nipples it seems not to be the case. The threaded portion of most nipples is at the top regardless of length.

I don't use it any more. The BHS linked one is quicker and works fine.

[wrcompositi]

In the case of thin spokes(DT Revolution, Sapim Laser or bladed spokes of equivalent weights) and high tension(rear DS), it's more convenient to use DT's calculator, which compensates for the elongation of spokes and rounds down the results. So in DT's calculator, Revolution's length(after correction) always rounds down even the result is like 260.9mm, while Competition's length rounds down only when the decimal is less than 0.5mm.

A 260mm-long 2.0-1.5-2.0 butted spoke, tensioned to 120kgf, will stretch by 0.9mm, which is not a marginal error if you're an obsessive wheel builder.

[bikerjulio]

it's more convenient to use DT's calculator, which compensates for the elongation of spokes and rounds down the results.

An interesting theory which I was not able to verify using their calculator.

It gave me identical precise lengths and rounded lengths for a rear wheel using either straight spokes or skinny butted 2-1.5-2.

It's an interesting point though that I don't recall being discussed. Perhaps I just haven't spent enough time on wheelbuilder forums.

[bm0p700f]

Use spocalc it is far better than the DT Swiss calculator as it is a spreadsheet and you can play i.e get it to work out spoke weights, do funny lacing patterns e.t.c

[wrcompositi]

Use spocalc it is far better than the DT Swiss calculator as it is a spreadsheet and you can play i.e get it to work out spoke weights, do funny lacing patterns e.t.c

I made myself a spreadsheet calculator which takes account of the elongation of spokes. May I call it "spocalc LIGHT edition"?

[stubob]

Well, after much more review, it looks like the best compromise build for the BHS rear is 1x DS heads out, 2x NDS heads in. Sheldon Brown's spocalc shows about 85% tension for the spokes and avoids some of the issues with radial NDS, especially 16:8. I probably will build these over the winter, whenever I have time and money.

[shimmeD]

Are you actually 2x the 8 spokes on the NDS and 1x the 16 DS, stubob?
Is it indeed possible to 2x the 8 NDS?

[Mackers]

1xDS has resulted in broken flanges on these hubs though.