Air bags on Utes , don't do it !

[Metters]

I can guarantee that that triton was overloaded- regardless of the weighbridge certificate, the fact he watched his load and the rest of his arguments
there is no way that that particular vehicle would have been under the rear axle load limit for the vehicle, even if under the GVM

I agree with you but the point is he thought he was doing the right thing and had all the aftermarket gear that he believed would enable the car to work that way.  That belief has come from product advertising and net forum advice.  He thought he was building a " tough Outback tourer"  and plenty of magazine stories have been based on those three words.

[Metters]

I can't see how any of them can be held responsible should the operator choose to overload their vehicle

My response still stands:

It is the use of many of these parts than can directly lead to overloading without the owner being aware of any developing problems

This is an interesting topic that may eventually end up in court one day but not necessarily in regards to bent chassis.  As far as I know they have not caused any accidents or loss of life but that may not be the case with suspension modifications.

I just looked through a couple of air bag company web sites and noticed all their information was about suspension adjustability, levelling and ride quality. I could not find anything on what air bags or heavier springs can do to the handling characteristics of the car, particularly at speed on sealed roads with big caravans tagging along behind. 

Have a look at these three links.  There are posts in them that have been written by two men who have both worked as car manufacturer suspension research engineers. What they are saying is nothing new.  It has been well known by suspension modifiers since the days before Sir Jack Brabham drove his first car.

Read the three brief posts by Collyn Rivers in this thread.
http://caravanersforum.com/viewtopic.php?f=2&t=59699

In this one he expands on it a little.  The whole thread that he started is very informative, particularly to trailer and caravan owners, but to cut it short read his last post on page three.  http://caravanersforum.com/viewtopic.php?f=2&t=22776&hilit=air+bags&start=40

Next read the post under it  by Robi.  This gets into leaf spring design.  Two posts later is a photo of a compressed  spring on a fully loaded ute.  Note what he says about it.

All of this seems to fly in the face of the notion of loading the car up then lifting it back up with an aftermarket product.  Cars are supposed to be down when loaded.

These suspension alterations affect all cars but dual cabs seem to come off a little worse.  I have read on a lot more than one occasion on the net that they do not have a good safety record when towing big vans.  They are usually a lot lighter than the big vans you often see them towing.  The wheelbase on many of them is not all  that long and the distance between the rear axle and the tow ball is about the longest of any type of car.  This gives the van a nice long lever to wag the car with. 

When you set these utes up with a suspension that has made the car more prone to swinging its rear end out in a corner, you start to see why their accident rate leaves a lot to be desired.

You could say it is still the owners fault, not the aftermarket parts manufacturers, but it reminds me of a report that I found in the State Library in Sydney seven years ago while researching a non automotive subject.  It was on the Rogers verses Whitaker medical negligence case in 1992.  Prior to this case a doctor was not considered to be negligent if he/she was following the standard procedures carried out by their peers.  The court reversed this and found the doctor guilty of failing to inform the patient of a very serious but rare possible side effect of the operation that he was about to perform.  There was nothing wrong with the procedure that he followed, it was just that he had a duty of care to inform the patient. 

Could the same apply to an air bag or spring installation company if a serious accident, possibly involving fatalities, was to occur and suspension alterations at one end of the car only were found to be a contributing factor and the company had not informed the car owner ? 

Only time will tell but that time could start getting a lot closer in the next month or two when Collyn Rivers releases his new book on caravan and tow car dynamics.  It is based on research information that he he has been compiling from around the world for the last twenty years.

When you change something on a car you will affect something else.   When that something else can lead to accidents or expensive vehicle reliability problems, I think the manufacturers of the parts or the installer has a duty of care to inform the customer.

[Hoyks]

I'm just looking at the impact mark in the middle of the chassis rail. I fitted new springs to my ute and i left the tails on the new U bolts sticking up. Under full compression, the strike mark from the un-trimmed U-bolt tail was fractionally aft and inboard of the contact mark pictured which I suspect has contributed to the chassis bending.

Upon reflection and getting dusty under my ute, under full compression that would see the bump stop squashed flat, the retainer plate that bolts on top of the spring pack would line up nicely with where the chassis has bent. I zoomed in and you can see that with the bump stop squashed, the forward edge of the top spring plate is folded up for strength, and this will probably will hit around 3/4" to 1" forward of the bump plate, which just so happens is where the rusty dent is. The load on the chassis would be coming down, the springs compress, the bump stop squashes and then all of a sudden the spring plate strikes the chassis. There is no more give available and the chassis bends around this new pivot point.

[noel_w]

So having just bought a Patrol ute with a steel tray 2400 long I am seriously reconsidering some options after reading this thread. I have planned to get an alloy canopy which I was going to put a wheel carrier on the back of it. That is now in question and has me wondering why I didn't think of this problem before. I guess seeing so many canopies built like this you think "that must be ok as others have done it.
I know having a steel tray is seriously heavy compared to an ally one but that is what came with the ute. The floor of the tray is removeable as it is held in place by bolts. Maybe removing the floor before the canopy goes on will be an option if it is designed to sit on the tray cross members thereby removing some weight.
The ute has had the coil springs removed by the previous owner and has an airbag system (springless) installed. It rides really well but had a chat with the "air bag man" on Friday who informed me that it would have to have new air bags in it to get a suspension lift at a cost near to $1k. Going back to springs sounds like a better option to me especially at a $400 cost if a bag gets a leak.
Back to the drawing board and some serious culling of what will go into the canopy.
I guess one question should be asked is it better to have a heavy trailer than load up the tray (within GVM limits)

[Hoyks]

A patrol ute is a better option for load carrying than these dual cabs. The way the load is transmitted into the suspension differs somewhat too as (most) of the Patrols I have seen are coils, rather than leaf sprung.

Look where the wheels are on a Patrol, they are almost centrally under the load. Most dual cabs the wheels are at the back of the cab and the load area is aft of that. Dump a big load down the back end and they try and lift the front. Because of the weight up front, this isn't going to happen and something gives in the middle.

Don't expect a 1 ton ute to actually carry a full ton and pull 2 ton over all roads and it should be fine.

[Elky]

The patrol utes also had issues with chassis cracking around the coil spring perches when loaded up and subjected to rough repetitive roads, usually at the upper end of carrying capacity, and from what I know many were overloaded too

[Hoyks]

The patrol utes also had issues with chassis cracking around the coil spring perches when loaded up and subjected to rough repetitive roads, usually at the upper end of carrying capacity, and from what I know many were overloaded too

It is an issue, but it is fixable and preventable, just google patrol coil tower brace and there are a few options to fix it.

[noel_w]

Mine already has a Superior Engineering cross brace that ties the chassis rails together. Already installed when I bought it - score