I recently managed to get my hands on a set of 16x7.5 et 20 hartge rims, or so they were sold to me. I've found a Hartge catalogue and it has no listing for any 16x7.5 et20 wheels, only et25. I want to widen 2 wheels for the rear but want to be sure of the correct et and also what size dishes I have now.

I found a guide online that shows to measure between the beads, this roughly measures about 7.5" so I'm pretty sure they are 7.5J wide.

I did a quick sketch in cad with my measurements and get ET25 which is spot on what hartge list!

I don't quite understand how to properly measure the dish though. It has a step back on itself and I'm not sure how to measure it right because of this. Measuring them like below their 1" and a 1/4

At a guess I would say they are 1.5" dishes?

I'd like to widen them though to 9J and so really need to know the size of the original dishes. Also to got from 7.5J et25 to 9J am I right in saying they become ET6?