Building straight pull spoked wheel, calculated spoke length is too short:(((

[peligro]

Rim is Mavic Open Pro Disc erd 595 (verified by measurement)

Hub is an unbranded 24h straight pull centerlock 100x12 front.

Measured with calipers.

Center to Left Flange: 27
Center to Right Flange: 35
L and R PCD 40

2x lacing

Two different spoke calculators gave the the same figure ~289. I bought 290s and the spokes are too short to even lace up the wheel.

I have built ~10 j-bend wheelsets over the years using random calculators and never had an issue. I triple checked my measurements. The spoke heads were all seated correctly.

What am I not understanding here?

[Aesch]

Did you use a straight pull compatible calculator?
When I put in your measurements, they do end up at 288/290.

Maybe a lot of offset in the spoke seat? That wouldn't explain the fact you can't even start lacing.

[peligro]

I think you are right that offset is the issue. I can't think of another explanation.

The DT calculator gave me the same length in both straight and j bend mode.

[UpFromOne]

Most spoke calcs don't actually factor in that a straight pull hub with spoke tabs locates the opposing spoke ends at the same point.
As opposed to equally spaced holes around the flange.
That issue can add 3-4mm to the spoke length.

[MichaelB]

I'm having a similar issue in rebuilding a pothole injured Hunt Carbon Areo 30 rear wheel.

Based on some info from the Hunt website, I didn't order the correct rim and so the existing spokes are too long. BUT, using the data from Hunt (Hub & Rim dimensions and existing spoke lengths) and using the DT Swiss calculator, don't cget correlating results.

So going to disassemble the wheel againm and remeasure using this site - https://spokecalc.io/measuring-a-straight-pull-hub.php - and the methodology that he uses to measure rim ERD (another page).

He also mentions how to measure the spoke offset (Dimension H is the one I think you are referring to)

[svendsvin]

If the opposing spokes connect to the same flange/point (like the picture above) you should input 2.5x lacing (and not 2x lacing). The dt swiss calculator can do fractional crossings. But also remember to still add spoke offset