What the NZ/OZ spec for a Phase II 172?

[RSZWEI]

My Father has just purchased a 2003 Phase II 172 and Im wondering what is the difference between the the New Zealand/Australian spec cars compared to the UK/European spec cars?

I believe that the NZ/OZ spec Phase II 172 have 15 inch wheels instead of 16 inch wheels (same design) as the UK/EU cars, does anyone know why this is? What size wheels do they handle better on?
Also, what is the offset (ET) of standard Phase II 172 wheels? Is it ET40?

 

[Fred@BTM]

ET48.5 the only difference was the wheels, best setup is 15's in ET 38

 

[RSZWEI]

ET48.5 the only difference was the wheels, best setup is 15's in ET 38

So the 15's are ET48.5? And ET38 is for the same designed 16's? Or is ET38 the ET of a Trophy or something else?
We are looking at getting some OZ racing wheels for it, but the one on offer are 15 inch, with an ET40. I guess they should be fine?

 

[m4tt274]

why did they alter the offset?

 

[RSZWEI]

why did they alter the offset?

Id like to know this as well.

 

[Fred@BTM]

in the uk the stock offset it ET48.5 on the 16inch 172 phs2

on the 172 cup they went to ET38.5 (so 20mm wider overall)

and on the 182's they went to ET45