Escort mk4 '89.
Yes, good point. Width of the tyre wouldn't change the arch rubbing when under load regardless of profile/hight. I guess a bit of arch rolling might solve it.
One job I do need to do which will affect this, I need to un-lower the rear or at least bring it closer to what it should be. Previous owner stuck some springs on it which has dropped it quite a lot (but only the rear). Too much for my liking.