If I went on to fit them based on this (your) advice and then had a legal issue... Guess who just became liable :cool:
So Porsche fit them to vehicles, irrelevant, they are engineered to use them... And dont have a 3500kg towing rating or as high a GVM :cool:
The CORRECT way to do this, in Australia, is to get the maximum legal offset rims to suit the vehicle...
Even the XR6 should have! Wheels are cheap as chips now.
Back on the issues...
The current D2 you have you wheels on came with 16" rims I believe, and you've fitted your 18" rim/tyre combo, correct....
You still would then have the 16" steering stops! Just undo them, fit a washer or 2 and re-fit, this will space them enough to prevent rubbing.
Even with offset rims the turning circle wont improve enough to justify the cost!
Your call - $0.20 worth of washers or a few hundred in adapters (and associated legal issues)..
Note: The 4" lifted Disco2 weighing 2700kg running 33" Muddies on factory 18" rims is a very stable machine, even on maximum side slopes... No extra track gains required...

