Notes on increasing GVM

[group3j]

Howdy,

I'm currently looking at increasing the GVM of my Nav as I know that I'm either close or over the limit when we travel. After a bunch of digging around on the Intenets I'd not been able to find any empirical information on the subject; only opinion and conjecture. I've subsequently spoken to a certified automotive engineer (I'm in Canberra, so folks in other states, take this with a grain of salt) and I thought post up what I've found in the event it saves other folks some time.

1. It is possible to legally increase the GVM.
A number of folks on various forums suggested it can't be done; this is incorrect.
A number of folks on various forums suggested that it can only be done through the installation of an approved kit prior to delivery to the customer. This is true in that some vehicles can have their GVM upgraded prior to delivery, but incorrect in the suggestion that only new vehicles can have their GVM increased.

GVM can be legally increased and certified through an appropriately accredited automotive engineer. I don't currently know all of the work that needs to be done to a D40 (I'm meeting the engineer next week), however form our initial discussion it would appear that it requires the application of strengthening to the chassis, suspension upgrades and the fitment of tyres with the appropriate load rating. I suspect it may also require brake modifications, but I'll confirm once I've seen the engineer.

2. The increase is reasonable.
Those posts I did read that suggested the GVM could be increased gave figures ranging from ~200kg's to 500kg's, depending on model. The engineer I spoke to owns a D40 that has had it's GVM increased and it is now at 3500kg's. I'm unsure of what model he has, but even assuming a factory GVM of 3010, it is still around 490kg's. At this point I think it is important to reiterate that this figure is achieved through strengthening the chassis - not just fitting bolt on parts.

3. It is expensive.
The ballpark figures the engineer gave me are as follows:

- Engineering/certification: $2K
- Plating/mechanical: Up to $10K

I believe the welding has to be done by someone holding a ticket and to an appropriate Australian Standard. So, being handy with mechanics and metal fab, I'm hopeful that I can save a big fist full of cash by doing everything bar the welding myself (have welders, just not a ticket).

4. There are cheaper options, but their ability to be certified by rego may be questionable
Some companies are now doing "GVM upgrade" kits, which essentially amount to "ADR approved suspension". Some of these are certainly kosher if fitted to a new vehicle prior to delivery, however their ability to legally increase GVM when retrofitted to an older vehicle isn't clear. In some cases, some kits would not appear to provide a compliance plate which leads me to wonder about their legitimacy/legality.
For folks in WA, you seem pretty fortunate, as number of places do kits which include a new compliance plate (e.g http://www.westcoastsuspension.com.a...g-gvm-upgrade/).

In all cases where you're considering retro-fitting them to a vehicle you already own, make sure you talk to your local RTA folk, as it all sounds a little hit-and-miss from the research I've done.

Finally, for anyone in Canberra, if you want the details of the particular engineer I've been speaking to PM me and I'll send them through.

I'll post more info as it comes to light.

 

[d22dave]

The country fire authority has done it to dual cab hiluxes in Victoria. Dont by who.

 

[Old.Tony]

Thanks for that info!

From what I'd read, the trick is to not exceed 3500kg. Vehicles over 3.5T attract some extra costs, so stopping at 3495Kg seemed to be the trick.

Upgrading the GVM does NOT upgrade the GCM if the GCM is stated by the manufacturer. That might be open to interpretation by a vehicle inspector, so here's the contentious bits:

1) Vehicle has a GVM of 2980Kg and is allowed to tow 3000kg with a stated GCM of 5980Kg. Increase the GVM to 3495Kg but since the GVM is 5980Kg, the max towable mass drops to 2485Kg.

2) Vehicle has a GVM of 2980Kg and is allowed to tow 3000kg but has NO stated GCM anywhere. You should be able to tow 3,000kg still - bringing your GCM up to 6495Kg.

The GCM won't be listed everywhere, but if it exists, there's not a single authority in Australia that I've found that will allow the GCM to be raised, so if you have a specified GCM, your towable mass MUST decrease if you increase the GVM.

I'd love to hear news - or better still, the relevant sections of the regulations - to the contrary.

 

[Luke86]

Definitely looking forward to your findings mate.
I just tend to think everyone is oblivious to the old gvm issue.

I'm running 145L long range tank. A full set of custom ply draws with upgraded roller system.
ARB bull bar and winch phegasas canopy, rhino roof rack and awning. Dual battery etc.
The typical touring setup I would think.

Was at the tip the other day with the box trailer on and broke in at 3t. trailer is 250kg approx.
plan to head back soon with an empty load and full tank of diesel.

Cheers
Luke

 

[group3j]

Hey Luke,

I've replied to your PM with the engineers details.

Yeah, I went to the tip last week with my truck configured exactly how I drive it around (driver, full tank of diesel, full recovery gear, etc, etc). I went to the weighbridge at the Mitchell tip and it came in at 2.76 tonnes; it's plated for a GVM of 2805kg's. So, driving around with just me in it, all is well. Add a wife and a child; over GVM. Will pull out the recovery gear and remove the roof rack this weekend to try and get things a bit closer to what they should be, but I doubt it'll be enough.

I had to reschedule my meeting with the engineer, but I'm booked in to see him this coming Monday (16th). I'm pondering replacing my Nav with a Patrol, so I'll be talking to him about GVM and lift engineering for both vehicles. Interestingly, he told me a GU Patrol wagon is likely to be over GVM with a bull bar, full tank of juice and 2 passengers, if you leave the third row of seats in. :-O Removal of the third row of seats get's you 160kg odd back on paper, though in practice it may not be the case. Apparently Nissan under-spec'd the GVM when they brought them into Australia, meaning that if you mod one and want to be legal, you need to engineer it.

I never would have thought GVM would have been an issue with either dual cab ute or a 4WD wagon when I started getting interested in 4WDing.

Anyway, I'll post up what I find post-meeting on Monday.

 

[Luke86]

Mate,
We must have been at the Mitchell tip on the same day.
I went there with a box trailer and I tipped the scales at about 3t!

I thought it must have been a heavy trailer I borrowed, turns out it only weighs 250kg, Ill be heading back to the tip on the weekend for round 2 without a trailer.

Looking forward to your findings!

Cheers
Luke

 

[group3j]

Rigthto,

Before proceeding, I just want to put some caveats on the information that follows:

- I can only vouch for the validity of this information for the ACT; I'm not sure whether it applies to other states and territories.

- The information was provided by a qualified and well-respected automotive engineer who has certified quite a lot of vehicles within the ACT. However, I'm not fully across how ACT rego evaluates engineering certificates, nor whether there is a standardised list of modifications for increasing the GVM of a D40. On that basis, the requirements below may not be the only way to increase the GVM of a D40; other engineers could plausibly recommend alternate approaches.

- The modifications listed below are not an arbitrary guess by the engineer on his requirements. He owns a D40 and it has been certified and approved by ACT rego to a GVM of 3500kgs.

- Finally, the notes below are my interpretations from the conversation I had with the engineer. Do not take them as gospel, but as a general guide to what needs to be done. If you need precise information, PM me and I can provide you with the engineer's details. (Note he charged me $150, though I requested ongoing advice which is covered within that payment).

Ok, with the clarification out of the way......

There are two key modifications required to engineer the D40 for an increased GVM in the ACT; chassis reinforcement and supplemental, self-leveling airbags for the rear suspension.

Chassis reinforcement must be applied to the bend in the rails that occurs in the area around the rear of the cabin and the front of the tray. It must be applied to both sides of both chassis rails and extend from the horizontal section of the rail around the tub mounting bracket, down past the bend and under the back of the cabin. The reinforcement on the engineers truck looked to also extend down under the floor somewhat, incorporating the front leaf spring hanger. Sorry I can't be more exact than that, but I was more concerned about the suspension side of things (see below). I also didn't get the exact specs of the steel or the standard required for welding, however it looked like 5mm thick mild steel and it had obviously been professionally welded.

As mentioned above, the second specific modification required is the installation of self-leveling airbags to supplement the rear springs. Note that these are *not* Polyairs or equivalent, but the same style of airbags that you see in trucks. They must be fitted in a specific location (which was immediately under the chassis rail, if I recall - apparently some folks try mounting them inboard) and must be connected to a pneumatic system (the engineer used a Landrover factory compressor, IIRC) that is controlled by a load sensing switch. The purpose of the self-leveling function is to ensure the vehicle handles sensibly with a heavy load and has the bonus of keeping rego happy through ensuring the headlights are always level.
This modification appears to be non-trivial and I queried the engineer as to how it would affect the offroad performance of the vehicle. He was of the view that the impact would not be significant, though I would have concerns on its affect on articulation.

In addition to these specific modifications, the vehicle must also be able to pass several handling and braking tests. From my discussions with the engineer, it sounds like the most common test for 4WDs to fail on is a slalom style test, where cones are placed along a straight length of road and the vehicle is required to negotiate them at 110kph. I can't tell you what equates to a pass or fail on that test, only that if you're running big tyres and lifted suspension, it's likely to be more of a challenge. This was relevant to me, as I wanted to exceed the 50mm lift barrier as well as increase the GVM.

Having looked at all the work done to the engineers Navara, I can see how he came to the $10K figure. That said, if you're handy in a shed and know (or are) a qualified welder, I've no doubt you could do it all for several thousand dollars less than that figure.

Finally; even if you're half serious about pursuing a GVM increase - talk to an engineer. One thing that has become very clear to me throughout this process is that the devil is in the detail. So many things seemingly need to be done to spec and any one of them could potentially cost you a lot of money if you get it wrong. Things like the type of material used for reinforcement, location of the reinforcing plates, process and certification for welding, type of airbags, type of self-leveling switch and so on. Find a reputable engineer, pay them some money and get them to help you work through the process. That's what I'll be doing.....just not with my Nav.....

 

[group3j]

Mate,
We must have been at the Mitchell tip on the same day.
I went there with a box trailer and I tipped the scales at about 3t!

I thought it must have been a heavy trailer I borrowed, turns out it only weighs 250kg, Ill be heading back to the tip on the weekend for round 2 without a trailer.

Looking forward to your findings!

Cheers
Luke

Passing ships mate. No other Navs when I was there.

I'd certainly be interested to hear what mass you come back with.

I've decided to pull my recover gear and some other stuff out and swap the steel cable on my winch for rope. Hopefully that, along with a few other bits and bobs, will get us back below 2.7t, which would be nice.