here is the VSB
http://www.infrastructure.gov.au/roa..._2011%20v3.pdf

notable parts
"The overall diameter of any tyre fitted to a passenger car or passenger car derivative must not
be more than 15mm larger or 26mm smaller than that of any tyre designated by the vehicle
manufacturer for that model."

"Speedometer accuracy must be maintained for the selected tyre and rim combination to within
the degree of accuracy specified in ADR 18 where applicable. It is suggested that the degree of
accuracy is in accordance with the most recent version of ADR18."

"Tyres fitted to passenger cars or passenger car derivatives must not be more than 30% wider
than vehicle manufacturer’s widest optional tyre.
The rim width must not exceed the recommendations for the tyre fitted.
For example, if the original widest optional tyre is 185mm, the maximum tyre width is 1.3 times
185mm = 240.5mm, i.e. a 235mm wide tyre. The maximum rim width for a 235mm tyre is
9 inches if the aspect ratio is 60 or below."

"The wheel track of passenger cars (or derivatives) must not be increased by more than 25mm
beyond the maximum specified by the vehicle manufacturer for the particular model. This
means that the rim offset must not be changed by more than 12.5mm"