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Old 16-09-2018
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Question Legality 31x10.5 + Lift, specifically TJ and Victoria

Started a new thread as 2" lift and 31x10.5 is a popular combination and didn't want to hi-jack or get confused with all the other lift and tyre combinations.
And I made a couple of mistakes in my previous.

First the lift kit, then the tyre discussion.

I think Victoria is allowed 50mm lift + 25mm tyre lift without Engineering.
I looked up these TJ vehicle details at http://myrta.com/rvd/searchRVD.do

Standard TJ 2003
P225/75R15 with +32mm Rim offset, Wheel track Front and Rear 1473mm
Unladen vertical measurement wheel centre to top of wheel arch.
Front 455mm, Rear 485mm

I bought my Jeep with a 2" lift detailed.
My Jeep measures 540mm wheel centre to arch.

If I focus on the front 540-455=85mm that was not a 2" lift kit, more like 3.5"

So at this point I blow the 50+25=75mm and already need Engineering.

Then I considered lowering to get back under 75mm.
As I read a bit it seems the max wheel center to arch increase is 2" 50mm.
And the max tyre increase is 25mm.

So I worked out the 31x10.5 increase for interest.

Stock rim = 15 inch = 381mm (rim only)
31x10.5 = 31 inch = 787.4mm (whole wheel and tyre diameter)
787.4-381= 406.4mm this is the two sidewalls of the 31x10.5 tyre
406.4/2 = 203.2 mm this is one sidewall of the 31x10.5
Stock tyre = 225x75 = 168.75 one sidewall

Stock tyre one sidewall - 31x10.5 tyre one sidewall = 203.2-168.75= 34.45mm

Did I do this wrong? Can't see how a 31x10.5 would ever be allowed in Vic??
It exceeds the 25mm allowable tyre lift.

And.. My Jeep would be a total increase of 85mm body + 34.45 tyre = approx 120mm total lift

So HELP... any informed answers would be appreciated.

Is the 50 lift +25 tyre lift without engineering correct?
Can I actually get 120mm Engineered?
What level of Engineering is this - a static inspection or the full swerve test?
Are 31x10.5 tyres ever actually legal on their own or even possible to engineer on a TJ?

All only in Victoria.
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Old 16-09-2018
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Hey ajftj,

All state modifcation laws are based on NCOP
(National Code of Practice for Modifying Light Vehicles)
This is better know as Vehicle Standards Bulletin 14

VSB14 can be downloaded here
Just a matter of searching Vic Roads website for your local interpretation

In particular you will need to understand LS7 - LS9
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Old 16-09-2018
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Quote:
Originally Posted by ajftj View Post
Did I do this wrong? Can't see how a 31x10.5 would ever be allowed in Vic??
It exceeds the 25mm allowable tyre lift.

And.. My Jeep would be a total increase of 85mm body + 34.45 tyre = approx 120mm total lift

Is the 50 lift +25 tyre lift without engineering correct?
Can I actually get 120mm Engineered?
What level of Engineering is this - a static inspection or the full swerve test?
Are 31x10.5 tyres ever actually legal on their own or even possible to engineer on a TJ?

All only in Victoria.
Technically speaking, no, you cant run 31 inch tires on a TJ because a LT225/75R15 = 28-1/2 so this would mean you can only go two sizes bigger to a 30-1/2.

It's easy to see how it's up for interpretation when a 31" tire actually measures about 30-1/2, nevertheless,
as I understand it, the popo only allow you to fit two sizes up from the largest size displayed on the place card inside the passenger door jamb.
A quick check of the size displayed on the sidewall and unless you have a blue sticker that's been passed by a Vic roads inspector that says otherwise, the popo let the canary out of the cage.

Another ridiculous law for the nanny capital of the world, but nice post, you've managed to articulate a relevant and pressing issue for many Australian TJ owners, well done.
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Old 16-09-2018
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Quote:
Originally Posted by Struth View Post
Technically speaking, no, you cant run 31 inch tires on a TJ because a LT225/75R15 = 28-1/2 so this would mean you can only go two sizes bigger to a 30-1/2.
yes, unfortunately this does seem to be correct

BFG list their 225/75R15 at 722mm dia
and their 31x10.5R15 are 775mm dia being 53mm or 26.5mm lift

this is a good example of what happens when idiot pen pushing non technical minded bureaucrats make technical decisions

I'm also at the ridiculous situation with my 70 series LandCruiser

the lower spec Workmate comes with skinny tyres the equivalent to 33" diameter. my GXL comes the wider but smaller diameter to the equivalent to 30.8" diameter. Legally I cannot upgrade to the same diameter as what is on the Workmate event though except for cosmetics, they are the same
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Old 17-09-2018
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ren0vator - thanks for the link to VSB14, I read it, it's very clear, and a little depressing, but at least I know.

Struth, bonza - always good to get some feedback on here and you are both pretty active contributors, even confirming what I thought, unfortunately - thanks all the same.

I don't really want any Police attention and I kind of like the idea of being insured. I do wonder after the dust has settled in QLD whether VIC will have a little go too. We do like our rules down here, and there are quire a few people who don't like 4WD activity.

So in summary for the record..

Is the 50 lift +25 tyre lift without engineering correct? [Yep - Afraid so]
Can I actually get 120mm Engineered? [Yep - but probably not worth the $ for the % serious offroad use I do]
What level of Engineering is this - a static inspection or the full swerve test?
[Full dynamic test]
Are 31x10.5 tyres ever actually legal on their own or even possible to engineer on a TJ?
[Not legal]

I was planning on some new tyres this year, so I guess I will go with something that is within the limits, but probably go for actual muddies rather than the existing slippery AT's.

New springs around $400 for a 2" set of 4. Might be able to recover a bit of cost on the existing set second hand as they were from DBOR and give a genuine 3.5".

Guess i'm going a bit soft.
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Old 18-09-2018
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NP ajftj,

Almost all the popo down here are pretty decent blokes/chicks and wouldent give a TJ with 31's a second look, provided nothing sticks outside the guards, your running a OEM or an ADR approved front bar and no looking for attention.

You could run two sets of wheels and change them over when you feel the heat. Also worth considering...

Option 1
Subtract the lift height of the 31" tires you want to run from 75 mill and try to bump stop and grind your way there with your lift, add some heavy bars/racks, whatever it takes. If you can make that work you can get an engineer to sign off on the tires without a swerve test, typically about $600 bucks if you do all the work and show the proof of the OEM specification against your modification.

Option 2
Take out finance, spent ten or so on a 33" engineered setup.
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Last edited by Struth; 18-09-2018 at 05:09 PM.
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Old 18-09-2018
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for the record I run 31" BFG muddies and a 45mm lift, thus giving me just under 75mm total

stock front bar with all the plastic bits removed and a winch bolted to a winch plate

never been hassled by the cops or questioned over the past 12 years with this setup
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Old 15-10-2018
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Ill throw this in, as I researched the crap out of this years back. As above. 2inch lift ok. 31s not ok - 30.5 ok (as said above for specifics ill not recover).

50mm in lift via suspension, with 50mm, change in diameter with tyres = 75mm total lift.

You'll need to stick with the 30s mate. However, just run 31s, you'll not be pinged.

ADR front bar you can run the uneek baja, its ADR. I do.

However, I run 3inch lift and 33s. I have the wheels in side guarsds and have mudflaps. SYE, breaks upgraded, 4.88 gears (4 speed auto) everything is done right and looks solid. Only looks big once you park next to a stocko..

End of the day, what ever your comforable with and make sure its done right If you're gunna sweat bullets driving past the cops with 31s, keep your 30s. and drive it
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Old 15-10-2018
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As I needed new rubber anyway I went for the 30's they fit within the standard arches.
I got the BFG KM2 Muddies and I think the benefit they will give me offroad over my crappy AT Kumo's will outweigh any loss from the reduction in clearance / tread width. They also look great😀

Will be interesting to see how they go on-road in the wet.

A set of King springs were just over $315 with one of the eBay 20% discounts and I fited them up over the weekend. They give me 40mm over standard.

I might be able to sell the ARB springs to recover some of this.

Overall it's pretty legal now, about 10mm lower axle and 15 lower chassis, really no big deal to be honest. You're right, unlikely that I'd have been hassled. Maybe my son on his Ps would be a different story, just not worth antagonising anyone. Also for him, now fully insured which was one of my worries.

I lowered my 4x4 😞
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