4X4 suspension modification laws; ‘Suspension Manual’ published

4X4 suspension modifications

Duncan Gay, the minister for Roads, Maritime and Freight, has just released the ‘Suspension Manual’ document, which is the new rules for 4X4 suspension modification laws in New South Wales.

Why do you need to know about it? If gives clear and concise guidelines on what’s legal, what’s not, and what needs engineering. We’re crossing our fingers (and toes) that this becomes the basis for a national code of suspension modification laws for all Australian 4WDers.

Navara NP300 TJM bullbar
Suspension lifts are a great way of improving your off-road capability, providing it’s done well.

This story follows on from our recent story about suspension law changes.

You can look at the manual here. Otherwise, read on for the juicy bits:

Minor Modifications

‘Minor modification’s are things that don’t require assessment or engineering before being deemed road legal. In other words, this is what you can do to your 4X4 before things get serious:

  • modifications to the suspension that does not increase or decrease the vehicle’s ride height by more than 50mm.
  • Changes in the diameter of the wheel and tyre combination of up to +/- 7% of the largest size specified by the vehicle manufacturer.
  • Modifications to the ride height up to 75mm that incorporate a maximum change in the suspension of 50mm, and/or an increase in the diameter of the wheel and tyre combination of up to 50mm.
  • Changes in the vehicle’s ride height by up to 50mm by replacing the rear coil springs with air springs fitted to un-modified, original mounting points when used with slow speed air controls in accordance with Appendix B.6.1a
  • Changes in the vehicle’s ride height by up to 50mm by replacing the rear shock absorber assemblies with air adjustment, fitted to un-modified, original mounting points, when used with slow speed air controls in accordance with Appendix B.6.1a.
  • Supplementary air springs that assist the original springs, and are fitted without other
    modifications, such as holes drilled in structural sections of a chassis.

This document of suspension modification laws effectively overrides VSB14, and gives 4WDers more scope for effective suspension modification.

Nissan Patrol suspension modifications
With a 50mm suspension and 50mm tyre increase, you’ll have a 75mm (3″) overall ride height increase.


If you’re dead-set on getting an engineer involved in your build, you’ll have to consult one if you:

Increases the vehicle’s ride height between 50mm and 125mm; or of up to 125mm that combined with an increase in the diameter of the wheel and tyre combination of up to 50mm increases the vehicle’s ride height between 75mm and 150mm.

These lawmakers aren’t much chop at writing effective sentences, are they? What they mean is: If you do a suspension lift of over 50mm, you’ll need an engineer. If you do more than a 50mm suspension lift and fit 50mm taller tyres (75mm total lift), you’ll have to get it engineered. Otherwise, you’re in the clear.

So effectively with these new rules, you have more room to play with overall ride height, provided that you use tyre diameter and suspension lift to achieve it. Body lifts are still off the table, as well as wholesale changes to suspension types, or modification of mounts or points.

The document goes to great lengths and pains to recommend people to thoroughly plan and research their modifications to their vehicle, particularly 4WDs destined for off-road tracks. For example, a 75mm lift through 50mm suspension and 25mm tyres will quickly evaporate under the weight of bullbars, winches, extra spares and other associated gear we all love on our 4WDs. So if you want to do an effective suspension lift that is a ‘true’ 75mm overall lift, you will need to look into stiffer and/or longer springs.

An extra note here: taller suspension does not instantly mean better off-road performance. Sure, your vehicle will be higher off the ground, but stiffer springs will reduce articulation and stability over rough terrain, and will put traction in a much shorter supply. Also, your centre of gravity gets worse, affecting your on-road and off-road performance negatively. If you’re keen on improving your off-road capability, static ride height is only one element you need to consider.

It gets a little bit tricky, however. Let’s imagine a big 4WD wagon like a LandCruiser or Patrol. You whack on a bull bar, winch, rear bar and twin tyre carriers. Let’s say, for argument’s sake that’s a total of 220-odd kilograms. You add this into your suspension mods, ensuring you have 75mm total lift with your extra weight. But then, for your daily commute, your remove one or two spare wheels, or you convert your steel winch line into lighter synthetic. You need to be aware that your suspension will effectively increase in height with these changes, and could potentially render it a ‘significant modification’, therefore legally requiring engineering. Like all good laws, this does become a bit of a grey area.

Toyota HiLux suspension modifications.
The trick for suspension modifications is accurately gauging what your vehicles and accessories weigh, and adding it into the equation.


I mentioned grey areas before, right? This document calls them ‘Tolerances’, and allows for changes in your height from changes in your tare mass, or slight variations in the modified components. The amount is 15mm, give or take. If you are in that situation of big changes in mass, whether it be full long-range tanks or whatever it might be, that gives you a realistic room to wiggle, which we think is brilliant.


Good question, and it’s one that’s answered by this significant document. It recommends you measure ‘arch height’ which measures the vehicle’s height via the highest part of the wheel arch. Or, you can measure ‘running clearance’, which is “measuring the distance from the supporting ground to the vehicle’s lowest point excluding unsprung mass. In taking the measurements, the vehicle should be supported on a firm, nominally horizontal surface, with the tyres inflated to the nominated pressure and the vehicle in the unladen state. The arch height or running clearance as measured should be recorded and photographed for future verification.”

Our opinion in this whole thing is that it’s a great step forward for the 4WD modifier. The laws have actually been brought into something of a semblance of real-world usage, making the laws relevant and real. 4WDers now can 100% legally commit to suspension any wheel/tyre changes that don’t make a big different to their safety, braking or handling. Big suspension lifts, body lifts and significant increases in tyre diameter still need engineering, which is still a good idea: road safety is very important, and the door is open for those who want to chase massive increases in off-road capability … it’s just going to cost them a bit more of the folding stuff.

What do you think about these new suspension modification laws? Have your say in the comments section below.


Click here to post a comment

  • Nanny State, nanny country I will never worry about what the authorities have to say my 4×4 , I have a two inch lift and 33″ muddies to bolt on for off-road. If they want to stop me they can follow me off road , not much chance in a divvy van

  • This is absolute bulldust. Why? You CANT impose the same regs on all vehicles!

    For example, put a 2″ lift and 31″ tyres on a hilux and you have a pretty solid and capable 4×4. It looks in proportion, rides very nice and if done with reputable components will be as safe if not safer then factory.

    Now go and put the similar deal on say an f250, Silverado or dodge and your truck is going to look no different from stock and is not going to help you off road either. So what’s the point? I’ve got a 5″ lift and 35″ tyres on my f250 and it is GREAT. Nothing looks out of place and I’ve had SO many cops tell me how much they love my truck. Funny, isn’t it….

    In the US, if your lift kit is less than 6″ most don’t even consider it lifted haha.

    My point is, if you do things to your truck that look way out of proportion it’s going to spotted and pulled to pieces. Most people can’t look at a truck and guess exactly what size lift and tyres are on it because there are so many variables such as flares, offsets etc. I’ve got a mate with the exact same f250 with cut out flares that you have to cut a few inches out of the guard to fit them. So it looks like it has a 6 inch lift but in fact only has 4. So how is measuring to his gaurd a gauge of how much the truck is lifted?

    So far from ridiculous, it ain’t funny.

  • my god what a load of bullshit,basicaly,we are in the 21 st century,i think,but obvioulsy not in this damn country,i think,my opinion only,as i dont have a gray area,every other country has modied vehicles,be it 4×4 or car or truck.the semi.s that came here from u.s. back in the 70.s,were detuned to conform to our hp rating.i was told.christ,please get out of this neanderthol mentality.even in u.s.,some states require you to have an insurance slip to prove you have it to drive your 12″ raised vehicle on the road you understand the principal of a pendulum,heavy bottom light top.i cringe when i see troopies raised with std wheels,a stiff breaze would blow them over.I for one have a high boy,raised 2″.its the highest 4×4 on the road std.what is it,the yank will know.its a 72-77 f250/350.brought here for the army & gov fire search ect.mining,yes its old but i dont buy the next model every 2 yrs becouse it now has 3 wheels not 2,pun,it runs 4.11 diffs std,35×12.5×16 wheels.twin lsd rear d60 lunchbox front d44,if it had the d60 front itd be an f350,only difference between them,why do i buy u.s. 4x4rs,there built right with enough power,not all parts same from 60.s to 98,so shit loads of parts.i nearly left the 4×4 club when it became law to only have 2″ combined lift.why bother.BIG thing i disagree with is if i took my toy/nis in for a 2″ lift,i would not get a brake line upgrade becouse its illigal for them to touch your brakes as a guy in the club foud out when we put it on the hoist,his lines were streatched to max,now is that safe,??? i beg to differ,the whole suspension needs to be upgraded.brake lines,breathers,track bar,pit arm.ect.go to y tube & look up dirt every day,AND LEARN SOMETHING.

  • Why don’t the sheep mentality media ever say there was a fatal accident involving two 2wd cars?We are so lucky in this free country that we have our brave fat arse lycra wrapped cafe latte greens saving our lives every day from our deadly and dangerous hobbies we choose.Get a real job you wankers one that actually produces something and stop making up bulls#$t laws to try and justify your existence.Thanks again my saviours

  • Easy fix. Vote for the Liberal Democrats next time. Senator David Leyonhjelm reckons every 4WD track should be open and you should be free to live your life as you please. Look it up, he’s awesome

  • ‘Suspension Manual’ document…

    btw, where is manual for HSV’s, FPV’s and other belly-scratchers with a massive 22 inch wheels and wrong size tyres on them, because people who fit/buy them do not understand offsets, rim flange size, rim width…

  • Paul, nice logic… We need comparison of bicycle VS motorcycle, 6m fishing boat VS Spirit of Tasmania ship… guess who is going to survive?

    Shall we all drive Barinas and Swifts? or perhaps 4×4 or even road trains? Just to be on a safe side…

  • Have you ever seen a vehicle with lifted suspension pull behind a Holden Barina or Suzuki Swift, seems that the front bumper rear/bull bar us almost a rear window height. Hate to think what migt happen is one such lifted vehicle rear-ended or ‘T’ boned a small car the occupants wouldn’t stand a chance.

  • Heavy springs doesn’t necessarily mean less wheel travel.
    If the springs are specified correctly for the constant weight that you carry then the suspension will perform correctly.
    Also if your springs are specified correctly to the constant weight you are carrying then you should still have the correct ride height that the suspension kit is designed for.

    It would be nice if these laws and guidelines acknowledge the commercially available kits on the market. If an Ironman 4×4 or ARB suspension kit is designed to lift the vehicle 2″s then this lift should be deemed legal even if some weigh has been removed from the vehicle during the week.

  • You think these reg’s are not so good ! try being a Hunter, and sporting shooter, and see how many hoops you have to jump through, and they are getting higher as time goes on. So now I have to contend with these laws, and reg’s as well, and I suppose they will get the same treatment. We are a suppressed society, and the dumb pollies are bound to make it even worse.

  • Why do we have to have so much regulation in our Country? I have just returned from the USA where you can do pretty much whatever you like to a vehicle. I have a photo of a Ford F250 with a 12″ suspension lift kit. Not my cup of tea but at least he had the right to do it. If these new restrictive laws were around in the early 1900s we would not have had the motor car industry in the first place. People like Henry Ford, Karl Benz and all the others would not have been able to make their first vehicle. Some will trot out the old “safety issue” chestnut when discussing these things. The way I see it, this will be just used as another revenue raising tool to harass the long suffering public, along the same lines as the speed camera. Don’t get me wrong, I am all for road safety. I work for the Fire Service and have done so for over 30 years. I have seen first hand a person get booked by a road side speed camera only to have a crash 150 metres down the road. No one was injured, but the point to be made is that the speed infringement did not stop the accident where as a police officer stepping out and actually booking the bloke would have. The bloke did not even know he had been booked until a member of the public went and got the police officer to come down to the accident site (she was unaware of the accident). With these regulations, how is the police officer going to determine the original ride height? Will he use a generic height as set out on the information brochure when the vehicle was purchased? Is each vehicle going to have an individual height measurement stamped on the Compliance Plate before it leaves the factory? Way too many variables for my line of thinking. There is a bloke up in Cape York who has built a 4×4 with a Land Cruiser chassis, Hilux body, big wheels etc. Under these regs, this vehicle would not be allowed on the road yet it would be, without a doubt, the most capable 4×4 in this country. We have too many laws as it is. We have gone past the point where we are a free country. This just adds to the problem with no net benefit other than an added cost to the four wheel drive enthusiast. No, I do not have altered suspension or a lift kit other than air bags on the rear in conjunction with the original coils.

  • still only valid in NSW. and measure to the wheel arch? What of flat fenders or pocket flares on Jeeps? Besides Jeeps have an interesting tyre placard. Doesnt state maximum tyre size just the size it left the factory with. National road rules? National gun laws? Hell they were talking about a standard gauge railway throughout Australia prior to World War 2 and we still dont have that. It appears that each state believes their elected and unelected public servants know better than the other states.

  • These rules are already in Qld 6in maximum lift but no more than 2in in wheels 2in suspension 2in body so its good that NSW is catching up

  • What about vehicles with ESC? I’m pretty sure the NCOP says maximum 50mm suspension lift only and no tyre size increase is allowed.

  • There are 50 shades of gray areas in some novels any several grey areas in government documents, otherwise it’s the only useful thing Duncan Gray Grey Gay has ever announced. Finally.

  • Height should always be measured on flat, level ground to ensure correct info.
    Glad to see one of the states is getting things sorted but we need a national code so there is no problems when you cross the border.

  • Today we are talking 50mm, but tomorrow it’s going to be 40…. 30… 20… nothing… all through the private engineer…. or through the government engineer. Road worthy maybe?

    You wont believe, but in 10 years time you will pay rego + % for your bull bar, towbar, side steps, mud tyres… Guess why? Well, somehow they need to rise money.

    PS So what about road safety? How someone else’s 50mm affecting you? Ofcourse you can say “well, what if…?” Well, it’s a “what if”, nothing else. What if some one drop a brick on you today, say from 5th floor? Should you wear a military helmet 24/7 or consult with an engineer (maybe doctor?) regarding strengths of your head?

    PPS mine 4×4 unmodified.

Get the latest 4X4 updates

Download Our Apps