IMO (and empirical experience) it's not just about the wheel/tyre weight/width or circumference, offset and % profile has a strong influence, particularly the former. IMO the car needs a high profile tyre (i.e. lots of sidewall height) to absorb all the little stuff.
I have 16", 17" and 18" front wheels for my car (all shod with tyres) and swap them round depending on conditions. I also swap around the ARB settings and offsets from time to time.
For the front, the 18" x 245 cause understeer, partly as it's hard to warn them up, and partly due to the necessary ET15 offset to get them to fit - this in turn causes scrub (which in turn (i think) causes the understeer).
Edited by Nev, 19 September 2018 - 06:47 PM.