Self-built wheel completely off-center
Issue:
The wheel I built myself is off-center, by approx 6 mm, as per the enclosed photo.
https://imgur.com/a/gAZEtBx
Explanation:
Had some leftover Rondo hubs and thought I'd try to build a set of wheels for my wife's Cube Nuroad. She's curious to go road cycling more, but we're not quite sure if it's enough to warrant a dedicated road bike, hence the wheel-building. If it's not yet obvious this was my first time building wheels. After much web-searching, measuring, calculating, ordering, waiting, assembling, swearing a lot, assembling, I finally had a set of wheels for her. The only thing that was left was for the wheels to be trued, so I took them to a local bike repair shop. They told me the wheels were fine, but that when they trued them, the rear wheel looked to be off-center by quite a bit...
Calculation:
I used both the DT Swiss and https://spokecalc.io/ calculators to make sure and measured and remeasured to be sure.
The wheels are built with DT Swiss G540 700C rims (non-offset). Spoke holes in both flanges are on a 58 mm diameter. Full width 142 mm, end-to-flange right 53, end-to-flange left 35, which gives left flange to center 36 mm, right flange to center 18 mm. Spoke hole diameter is 2.5 mm. 28 spokes, 2 cross, not straight pull. Both calculators gave results for both wheels between 278 and 280 mm spokes and based on what info I could find online, 1 mm +/- is fine. So, to make my life easier, I went with 279 mm spokes.
Can anyone please explain how this can result in a wheel being off by 6 mm? I just remeasured and recalculated everything and came to the same results. What am I doing wrong?