how much difference in tire size is acceptable Page 9

Short answer: don’t play fast and loose with rubber unless you fancy a moody speedo and ABS having a sulk.

As a rule of thumb, keep the overall rolling diameter within about ±2% of the OEM size; going more than one wheel size up or down is where trouble begins. Width changes of around +10–20 mm are commonly doable, provided you check offset and clearance, and always meet or exceed the placard’s load index and speed rating. Push beyond that and you invite rubbing, wonky handling, and potential grief with state regs and insurance in Australia. Before spending your AUD, have a reputable tyre shop confirm fitment and compliance for your state.