Old Man Emu 4015kg GVM upgrade kit

My general advice with for overland build projects is to make changes over time, so you can learn what the stock setup does (and doesn't) do for you. This is especially true for suspension, where getting the best performance requires you to match your springs and shock absorbers to your final axle weights. But for this build, I decided to do the suspension first. Here's why...

We have a weight problem

Like most 4WD wagons, Cruisers are critically short of payload, and the standard suspension struggles to cope at maximum load. They're better than some, but they're still not good enough.

Of all the new 4WD wagons currently on the market, only the 78 Series troop carrier has a payload high enough that you could feasibly use it for long range desert work without modification.

The 200 GX can carry 710kg in theory. In real life it's probably a bit less than that, because the manufacturer's claimed kerb weight is often a bit of a fantasy, like the claimed fuel economy.

I'm confident that the 200 is a very well-engineered vehicle, and I reckon 710kg is a conservative number that doesn't really reflect the vehicle's engineering or safety limits. The Cruiser has a much stronger chassis, stronger wheels, stronger tyres, heavier duty suspension, and much less axle overhang than a one tonne pickup like the Hilux, so it doesn't make sense that the payload is lower. I suspect Toyota are describing the design limits of the comfort-tuned factory suspension.

Even though my build plan is a work in progress, I know that between four occupants, a full load of fuel nudging 300 litres, a few jerry cans of water, an extra spare wheel, heavy duty tyres, and the bull bar and roof rack, I will definitely be close to that 710kg limit. Add in camping and cooking gear, recovery equipment, spares, and the ball weight from my trailer, and it will easily exceed 710kg.

So what?

The chances of being pulled over and weighed are pretty slim, and frankly the penalty if caught isn't huge. It's probably worth the risk - right up until you're involved in an accident. Then you can be sure your penny-pinching insurer, and possibly also the law, will suddenly be very interested in what your car weighed. Prosecutions are rare, but they do happen.

For the same reason I pay for home insurance I'll probably never use, I reckon it's worth a small cost to eliminate the legal risks of exceeding my payload. Especially since I would almost certainly end up changing the suspension anyway.

The solution: GVM upgrade

In Australia, the answer to this problem is called a Gross Vehicle Mass (GVM) upgrade. There are two ways you can do this:

• Buy a kit from an aftermarket manufacturer

• Design your own solution and have it certified by an engineer.

Unless you have very specific needs and a lot of time and money, buying a kit is the easier option. You can then opt to install your kit before first registration, or at any time afterwards.

L-R: Lovells Suspension testing rig; SSM compliance plate

Pre-registration GVM upgrade

Pre-rego upgrades are quite easy. You find one of several suspension manufacturers who have been certified as a "second stage manufacturer", or SSM. You buy their kit and have it installed by them or someone they approve. A new compliance plate is permanently fixed to the vehicle showing a higher permitted gross vehicle mass, and the modification remains good for the life of the vehicle.

The SSM takes care of the necessary engineering testing and approvals. In many cases, the product supplied in your kit is exactly the same as if you'd just asked for heavier-duty suspension from the same supplier, with the addition of the compliance plate and some paperwork.

Post-registration GVM upgrade

GVM upgrades done after registration are pretty similar, except that the approval process the SSM has to go through is a little different, and the change to your payload is certified by the state of registration. This means there are a couple of differences.

Firstly, depending on the kit you choose and the installer, inspection by a licensed engineer is probably required. The engineer will certify that the kit installed matches the approved one and it has been installed according to the kit manufacturer's specifications.

Secondly, the approval is achieved through your registration documents, so while some states will issue you a permanent modification sticker to put next to the compliance plate, should the vehicle registration ever lapse or be transferred to another state, you may have to have the modification re-certified.

Custom GVM upgrade

The third option is to do what you like, and have an engineer test and certify the result. There are a few things the engineer has to do, including swerve and braking tests, which means you need a specialist who knows the ropes and has the gear. You'll also need to hire a track, and maybe provide the engineer with technical details of your suspension components which not all companies are willing to provide.

Once approved, your GVM upgrade works exactly like a post-rego upgrade.

If you can find the right engineer and afford to pay for their time, this option lets you build pretty much anything you like. This is what Project 200 did for their upgrade, sharing the cost of the engineer amongst several vehicles.

Cost

The cost of pre- and post-rego upgrades is about the same (although note that if your dealer is following the law, in most states the cost of a pre-rego upgrade will attract stamp duty and luxury car tax if applicable). The cheapest I got quoted was around $2,500 and the most expensive was north of $10,000.

The cost of a custom solution is theoretically unlimited, but the major variable is the cost of the engineer and testing. There's at least a few thousand in that, unless you know a bloke or have your own track. I very much doubt this option would be worth your time unless you were willing to commit at least $5k to it, and probably much more.

My solution

I went for this pre-rego, partly because being able to transfer it interstate may boost future resale value, and partly because ARB can offer a slightly higher payload increase on the pre-rego kit.

The ARB kit allows for an increase to a GVM of 4,015kg, a 665kg improvement over stock. For the GX, that gives a payload of 1,375kg. This is so much more than I will ever need, it future-proofs the vehicle for any wild plans I might have later. It also improves the maximum front axle load to accommodate this increase, although I do not expect to need that and so I can't remember what the change is.

The ARB kit also changes the ADR design category from NA (light goods vehicle) to NB1 (medium goods vehicle 3,500kg-4,500kg). This necessitates the fitment of some rather awkward-looking rear-facing side indicators, which aren't amazing to look at, but at least might distract from the bulging, phallic snorkel.

Rear-facing side indicators, part of the NB1 upgrade

The kit came with the option of 400kg or 600kg constant rate springs, and I opted for 400kg since I won't be anywhere near the upper limits of this suspension most of the time. If I decide later to change to 600kg springs, well, that's still compliant with the approval.

The upgrade also came with the option of conventional Nitrocharger gas shock absorbers, or for a fairly hefty additional cost, remote reservoir BP51 shock absorbers. I've heard nothing but good things about BP51s and there's no question they're a quality product, but I've also been happy with the performance of Nitrochargers on several previous vehicles, and shock absorbers are a disposable component! Plus there's an argument to be made that the conditions under which I put the most demand on my shocks - slow, hot, and heavy corrugated tracks - are where the advantages of a remote reservoir system are least obvious. They rely on cooling airflow to deliver their benefits, which is why competition race trucks have the reservoirs hanging out in the breeze.

The price for the ARB kit was $3,300 with Nitrochargers and $5,800 with BP51s. The price difference was more than enough to pay for some other things I wanted, like six new tyres and an extra spare wheel. As the BP51s are approved for this kit, I can always change them later if I've made a mistake.

ARB provided before and after measurements (top of guard to top of wheel rim), which will be a future handy reference.

FL: 751mm to 823mm (+72mm)

FR: 749mm to 821mm (+72mm)

RL: 825mm to 872mm (+47mm)

RR: 825mm to 873mm (+48mm)

That front height is too tall to be legal, but the springs have been weighted anticipating the load of a bullbar and scrub bars fitted up front. I'll measure it again once those are fitted, but if it's still more than 50mm I'll need to do a diff drop. (Might be wise to do one anyway!)

Did I make the right call? Add a comment!