2014 JK largest tyre size legal in NSW

I know this has been asked many times before but Im still confused.
I want to put the largest tyres I can legally in NSW on my 2014 JKU Sport, So what's the biggest I can go?
My standard tyres are 245/75/R17 and when I look them up on Goodyear's tyre chart they are only 30.5 inch in diameter & 9.8 inch wide, as far as I know I can go 2inch or 50mm bigger in diameter, not sure how much wider I can go?
So that only allows me to go a 32.5 inch tyre?
I hear all the time the biggest you can go is 285/70/R17 but on a tyre chart for Nitto Trail Grapplers that is a 33.15inch diameter & 11.81inch wide tyre
Can someone please set me straight or am I on the right track?

275/70/r17

By calculation 245/75r17 = 31.47"

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What does "legal" mean? OK seems a stupid response, but this question has made bush lawyers out of most of us.

Start with the tyre placard on your JK. What tyre size is on that? If you get pulled by a zealous cop and your tyres don't match, you'll be called in to explain to engineering.

With certification the general theory is your tyres can be +7% (circumference I think) and a 2" lift, as long as you don't change your track width. That way the copper will see your certification when he dials in your plate number. This is often interpreted as 33" tyres and 2" lift is the max legal. With certification. And it kind of matches the various ADRs. Roughly.

If you're lucky you have an earlier JK (like mine) which has 255/75/17 on the door sticker. This equates to a hair over 32" :) so add 7% and you are over 34" legally. Also pretty sure that 7% is self certified, in other words legal without having to get certification. You need certification if you go bigger than that.

Cheers
Steve

The law is the law. 7% greater or lesser than the maximum size available for that model ((which is the placard). Not sure whether people get the 50mm rule from but as I understand it Lift is restricted to 30% of the stock travel of a vehicle. And in a JKU I believe that o be 9.25"


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