It's taken me a while to figure out what's going on with rear triangle spacing and alignment on this bike, but I see now what was done with the SS/FG conversion. What I don't understand is why it was done this way, and if I can do anything at this point.
For measuring alignment I used a string from the dropouts and around the head tube. Per the specs, the frame was originally 126 mm spacing. It's now 130. The driveside has been moved 7mm to the right (seen from the rear), and the non-driveside has been moved 3mm, also to the right. 126+7-3 = 130.
The wheel has a 120mm Surly SS/FG hub, not dished. There's a 10mm nut added to the drive-side axle as a spacer inside the dropout. 120+10 = 130.
The wheel can be flipped, the nut moved to whichever side is drive side, chainline is perfect, and the rim is perfectly centered in the frame.
Why did they do this? It works, but switching between SS and FG isn't as simple as it could be. All I can think of is, they had a 120mm hub, and this was their best idea of how to accommodate that hub. It seems to me a better solution would have been to move each dropout 3mm and use the 120mm hub without a spacer. Then switching between SS and FG would be straightforward, which is what I want. Makes no sense to me.
All I can think to do at this point is either just ride it as-is and carry tools when I might want to switch on the road, or (re-)cold-set the drive side a whopping 10mm to use the hub without spacer.
Last edited by downtube42; 11-10-22 at 11:31 PM.