Wish it was my scenario but this is straight from Holden and the regulators
As I’ve said before, it’s bureaucracy gone mad
My aim was two fold. First to gain a slightly more compliant daily ride by reducing wheel diameter and rear width while having same wheels front & back size (for better tire wear via rotation). Bonus is cheaper tires but that’s not the driver. Secondly, I don’t need nor can I even legally access the performance loss even with the narrower wheels on public roads, so putting the original staggered wheels in storage will protect them from any potential gutter rash (and I’d feel more relaxed parking in tight spots; auto park just seems unnatural). The other benefit is it won’t rattle the car to bits over the longer term (and it’s not as if I can drop tire pressure much on rubber bands).
The crazy part is narrower wheels were available in other variants but I can’t reduce rear wheel width to those sizes. Yet there seems to be no issue putting absolute shite tires on the existing rear wheels or going wider on fronts (if they fit). And the reasoning,... ABS calibration... sound familiar... Now that’s pure madness