How To Modify 4WD Suspension And Tyres Legally

After almost 100,000kms, the factory tyres on my 2010 PB Challenger are about due to be replaced. So I thought I’d start looking into Modifying 4wd tyres and suspension legally. I know that the majority of people just do it, but being a model citizen (cough) I thought it would be best to do it as legally as possible. After all, if you modify your car illegally then you run the risk of being issued with a yellow sticker by the police, and you also risk not being covered by insurance.

Lots of insurance companies will state that they cover 4wd modifications no matter what you do… as long as it’s a legal modification. Makes sense really… Why would an insurance company put their hand up to insure something that wasn’t legal. Makes no sense.

If you have an insurance company who has stated that they’ll cover your modifications then be brave, call them up and ask them if they cover modifications that aren’t legal. I bet they’ll run for the hills.

Vehicle Standards Bulletins

Vehicle Standards Bulletins (VSB) are a set of regulations put forward by the federal government. The federal government then encourages the states to adopt these regulations in their entirety. I’m in Western Australia and we have adopted VSB14 in its entirety. Some states have and some haven’t. Please check with your local authority to clarify what has been adopted in your state.

The VSB that we are interested in is VSB 14, which is the National Code of Practice for Light Vehicle Construction and Modification (NCOP). And more specifically, NCOP11 Section LS Suspension and Steering V2. At the time of writing this post, the last update to this document was in January 2011.

There is a whole lot of detail in the document that I found didn’t apply to my situation. Really all I want it to slightly change my tyre size from 265/65R17 to 265/70R17 and then lift my vehicle by less than 50mm. The total height change will only be about 47mm including tyre size and suspension.

VSB 14 as it applied to me

So I sat down and started reading VSB 14. The first thing I noticed was that there is a whole section outlining what modifications you can make without approval, what you need basic signoff for, and what you need further testing to have approved.

In this section of VSB14, it says that I’m allowed to modify my tyres, rims and suspension as long as the total height change does not exceed 50mm, that my total suspension travel is not increased by greater than one third of the original suspension travel, and that my modifications comply with Sub-Section 2 – General Requirements.

Ok so those first two requirements are easy enough for me to meet. I’ll just have to confirm about the suspension travel but I’m sure that’ll be OK. What’s this bit about Sub-section 2, though. What does that mean… Let me take a look…


Ok so this is where it starts to get a bit strange. In reading it I can see comments like “The roadholding and handling qualities of a modified vehicle must not be adversely affected”. Not 100% sure of what that really means or who decides what “Adversely Affected” really means… But anyway…

It then also goes into minimum road clearance, turning circles, etc. Then it gets really detailed and mostly not relevant to me… So I skipped over it.

And then I got to a section that is all about vehicles with Electronic Stability Control (ESC). ESC is a very important safety feature of vehicles. According to Wikipedia, ESC is the technology that improves vehicle stability by detecting and correcting for loss of traction. When ESC detects loss of traction, it automatically applies brakes to effectively steer your car back on track. Different vehicle manufacturers name it differently so check with your vehicle manufacturer.

Now my car, a 2010 Mitsubishi PB Challenger is fitted with ESC. And according to the Federal Chamber of Automotive Industries, “On 22 June 2009, the Australian Government announced the introduction of an Australian Design Rule, based on Global Technical Regulation No.8, for the mandatory fitting of ESC to passenger cars and SUVs from November 2011 (for new models) and November 2013 (for all vehicles)”.

The way I understand this is if you’re car is post 2011 then it has ESC. Check with your manufacturer.

So back to VSB 14, section 2.6…

Basically, this section outlines what ESC is and then says “For modification codes contained in this Section of VSB 14, evidence should be obtained either from the vehicle manufacturer or through testing to determine the impact on the ESC system. To remain within the scope of this Section of VSB 14, a vehicle fitted with ESC must not be modified if the operation of the ESC is affected unless the ESC system is adjusted accordingly.

Persons wishing to modify vehicles equipped with ESC must contact their Registration Authority for further information and guidance.”

Ok, no problems. I can just head down to the local Mitsubishi shop and ask them to prove to me that what I want to do is going to be OK… Right? *shakes head*… No…

Although it was pretty obvious to me what their response was going to be, I decided to ask Mitsubishi what they thought of me using non-Mitsubishi parts on my car… As you’d expect they came back saying that they don’t recommend using anything but genuine Mitsubishi parts. Of course they would.

So this leaves me with proving through my own testing what the impact on the ESC system is and then adjusting the ESC system so that it’s not adversely affected. How on earth do I do that? The ESC is controlled by the car computer! I can’t just hack into it and change ESC settings!!

Surely the WA Department of Transport will have more information on their website. And they do! It’s a great website that clearly outlines what you need to do. Because I have a vehicle with ESC, I found that I need to submit a vehicle modification application form. Which I did.

The response was basically that because I had ESC, I’d have to prove through testing that there was no adverse effect. And to arrange that testing I’d need to contact an engineering signatory and arrange it with them. I assumed that this would come in the form of a swerve test or lane change test. There is a great video of a Hilux performing a lane change test on YouTube:

But wait… If I want to undertake a lane change test, I need to get my modifications done first… What if it fails??? So many unanswered questions…

Anyway, there are a list of engineering signatories available from the WA department of transport. I contacted one with a general query about the process… Below is the conversation that I had with him (names removed)

From me:

I have been given your details by the Dept of Transport in regards to obtaining a signoff on modifications that I’d like to perform on my vehicle.
My car is a Mitsubishi Challenger 2010 fitted with Electronic Stability Control. My intended modification is to upgrade the factory suspension which will lift the vehicle by approximately 40mm.
Although it is within the general limits of what is allowed, VSB 14 says that I need to prove either through vehicle manufacturer statement, or through testing, that the ESC has not been affected.
If I can provide a statement from the suspension manufacturer that says that they have performed thorough testing on their product and have demonstrated that there is no adverse affect on the ESC, would that be enough to enable you to sign off on it do you think?
Thanks for your help.
His response:


In short, you have a snow ball’s chance in hell of getting this modification through, unless you have a very precise directive from the original manufacturer.   Otherwise, I would not touch it.



Ok so all I have to do is… No, wait… What? Let me read that again…

So if I can’t get a clear directive from Mitsubishi, a statement from the suspension manufacturer isn’t enough, I can’t modify my vehicles ESC settings,  and I can’t get an engineering sign-off, then what they’re telling me is that there is NO WAY to legally modify the tyres and suspension of a vehicle fitted with ESC? in other words EVERY CAR NEWER THAN 2011!

NOTE that this doesn’t just apply to 4wd enthusiasts… What about those people who want to lower their HSV or FPV? Are they doing so illegally? Surely I can’t be interpreting this correctly. This affects the entire tyre and suspension industry WA wide! And potentially in other states as well!

I would love to hear your comments on this! If you’re in WA or a state that has adopted VSB14, and you have successfully LEGALLY modified the tyres and suspension on a vehicle with ESC, and you have PROOF that you’ve done it legally then please let me know!!!

THINGS HAVE CHANGED! Read Modify tyres and suspension legally Part 2 for more information.

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