Here is the RTA rule. As you can see the max track increase is 12.5MM per side. I have never seen 12.5 MM spacers. My porsche had about 1 inch spacers.
An important requirement for all replacement wheels is that the wheel track must not be increased by more than
25mm beyond the maximum specified by the vehicle manufacturer for that vehicle.
Where non original axle or suspension components are fitted, the offset of the wheel in relation to the axle or stub
axle assembly used shall not be increased by more than 12.5mm each side of the vehicle based on the specifications
of the axle components used. If an axle assembly is shortened then the track width limit is taken as the axle
manufacturers original track dimension, less the amount the assembly has been narrowed, plus 25mm.
If you are contemplating fitting non original axle or suspension components you should seek the guidance of a
signatory as engineering certification will be required (see page 3).
If you want ot read the whole thing.
http://www.rta.nsw.gov.au/registrati...vsi09_rev4.pdf
Regard sPhilip A
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