Below is a link that will describe all the legal regulations for light vehicles and offroad vehicles for suspension, tyres, etc.
http://www.infrastructure.gov.au/roads/vehicle_regulation/bulletin/pdf/NCOP11_Section_LS_Suspension_and_steering_3Feb2006.pdf
http://www.infrastructure.gov.au/roads/vehicle_regulation/bulletin/pdf/NCOP11_Section_LS_Suspension_and_steering_3Feb2006.pdf