Hi all - I'm wondering if someone can help explain a calculation to me.

I have a crankset, with manufacturer specs of a 42mm chainline, and calls for a 110mm BB spindle (JIS) for "most applications" (it's a VO Grand Cru single). Meanwhile, I have an IGH, for which I calculate the chainline to be 49.5m (a modern Alfine 8, with cog dishes inwards).

In order to match these, do I simply add (49.5 - 42) = 7.5mm to the spindle length, and buy the closest one? That would be the 118mm BB.

Is the calculation any more complicated than that?

If anyone wants to comment on my number for the Alfine 8, or steer me in the direction of anything other than a sealed Shimano UN55 BB, I'm all ears...

Thank you!!