[Closed] Should you set spoke tension before or after tyre fitted and inflated?

yup specialized thick carcass jobbie.

its quite a lot of tension drop. about 20%

Never read Roger Musson’s book, have heard it’s good, but would suggest also that things have changed since the book was written a while ago…

What, like the laws of Physics? 😀

OP – I think you’re worrying over nothing.

This is the best advice you've been given on here.

I'd suggest building with tension measurement before mounting tyre, but potentially re-verify the tension is within acceptable range after mounting and pumping up the tyre if this is likely to have a significant impact - e.g. a tubeless road setup for a larger person who runs high pressures.