Tires - what is legal

[Fathead]

so have lifted my JKU 2.5" and now looking to upsize the tires from the standard 245's on standard rims

but unsure what is legal. have red lots of you can only legally go 2 sizes up without engineering ie 285. however i have also seen posts showing legal 295's

further complicating the issues is that not all tires are created equal ie: a 285 trail grappler is approx. 33.15 however a dura trac 285 is 31/32 and everyone comments on how the BFG's are small

so again what is legal??

[chris0375]

Well your 2.5 inch lift is possibly illegal.

Don't worry about people saying 2 sizes up. It's meaningless. You should really quote the full size. Most people can guess what you are talking about but quoting only width means I can't know for certain what size you are talking about. It's not like we are talking about shoes. It's based on the listed measurement. Not what it actually measures.

Look at your placard, work out the diameter, add 50mm. Then compare to the tyre you are thinking about fitting.

You are allowed 50mm up in diameter from what is listed on your tyre placard, at least in Victoria. Different wranglers have different placards. Older ones had smaller tyres.

Read relevant data to your state.

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[Wooders]

Usually 50mm increase in rolling diameter is the legal max without engineering certs/mod plates.

[Hanna]

It's illegal to use the word "tire" in Australia!! We use the Queen's English here, therefore "tyre"

Anyway, Chris has pretty much nailed it. Once you have checked the applicable laws in your State for the maximum allowed increase, just compare the labelled size of the tyre you want vs your vehicle's tyre placard and see if it complies. In terms of compliance, you really don't need to worry about the actual size of the tyre, just that the labelled size as sold fits within your limits.

I assume that you have the 245/75R17 GY Wrangler Silent Armours, which are approx. 31.5" (i.e. 245 x 0.75 x 2 /25.4 = 14.47" + 17" = 31.47") or 800mm, whereas 285/70R17 are 32.71" or 831mm. So if you are allowed to go 50mm bigger, you could go to a 295/70R17, which is 33.25" or 845mm.

Hope this helps?

[Fathead]

Thanks Hanna & Chris. Will check the label and go from there. But yes the 2011 jku currently runs the stock 245 75 17 (or 245 70 17)

sent from a clown with a jeep and phat fingers

[Clarky]

NSW now uses VSI 06 so its 7% larger diameter then the largest factory fitted tyre option.

Tyre width is limited by the rim/wheel width, rim/wheels can only be 25mm wider than the largest optional wheel recommended by the vehicle manufacturer so the tyre you fit must suit the rim size.
Wrangler's have a 7.5" rim so the max increase is to 8.5".
Also
•must be contained within the body work or mudguards (including any flares) when the wheels are in the straight ahead position.
•must not foul any part of the body or suspension under all operating conditions.

Offset can only be changed by 12.5mm.
Stock wrangler rim have a +44.4 offset so +30 rim is probably the closest you will get, a couple of mm's out but close enough.

http://www.rms.nsw.gov.au/documents/...ifications.pdf

As for different brands having different actual sizes this doesn’t matter as the RTA-RMS/police go by what’s on the side of the tyre not the real world size.

Here is a tyre size calculator that gives you the % increase over the stock tyre.
http://www.rimsntires.com/specspro.jsp

[Tyvokka]

Originally Posted by Hanna

It's illegal to use the word "tire" in Australia!! We use the Queen's English here, therefore "tyre"

Here here, because the Queen owns "independent" Australia.

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