Any Place For Air Suspension In Overlanding

[vwhammer]

I have been working on the design for a 4wd conversion for my van.
After thinking long and hard about how to suspend the vehicle, I can't seem to shake the thought of an airbag suspension set up.

My primary issue with continuing on with an air suspension is the comparative complexity over a traditional spring set up.
With this complexity comes the introduction of several failure modes that could be tricky to fix in any country.

Sure, I could design built-in-limp-home fixes that could get me back to civilization in the even that something fails but that only adds to the complexity.
I suppose the only real failure that could not be overcome easily would be a bag failure.
I guess I could carry an extra bag or two but that's just more crap the takes up space that would otherwise be open with a standard metal coil spring.

Now, one might be saying that over the road tractor trailers have logged millions of miles on air suspensions without failure so they must be pretty durable.
While most of this statement is true, truckers don't exactly see the harsh terrain that many overlanders or even the occasional trail junkie might see.

Before we get into whether bags have any place on the trail let me tell you why they appeal to me.
For starters, I used to design and build air suspensions for a living for cars and trucks off all sorts back when the mini truck and sport compact car craze swept across the US.

Secondly, I like the idea of being able to lower the center of gravity for on road and cornering stability then being able to lift the truck back up for off road mode.

Lastly, I also like being able to add a little air to the bags when the I am loaded down or towing to correct any sagging suspension issues that may arise.

With all that said I am a pretty big fan of the Less-is-more mentality so perhaps I should just let it go and just roll with a properly set up coil-overs suspension and enjoy the drive.

So, This brings me to my question: Does an air suspension have any place on an expedition rig?
I don't really have any immediate plans to travel the globe so most of my excursions will be in the US and Canada but the question still stands.

I am interested to hear some opinions on the subject.

 

[TeCKis300]

Are you proposing an air bag suspension as a primary (i.e. only) load carrier, or are you suggesting it as an auxiliary component to a traditional spring?

 

[vwhammer]

It would be the primary means of suspension.

 

[java]

I have seen a bag that fits over coil overs somewhere. It was 6-8" tall and went above the spring on the coil over. Could work like you want. Dump the bags for on road. Fill them for clearance off.

 

[mnfeo2]

I have the spring helper bags. I've been happy with them so far.

 

[vwhammer]

I am exploring the coilover bag/spring combo as it solves one major issue.

When using a bag only set up, when you let air out of the bag to hunker down for on road use you are also effectively losing spring force.
This means your suspension becomes all floppy for lack of a better term.
This does not equate to a well handling vehicle.

They do make some tapered bags that help this problem a little but most are not rated all that high as far as load carrying capacity is concerned.

Also most bags of any design in a size I can use do not have overall travel range I am looking for.

So this pointed me in the direction of the coilover bag/spring set up.
I can set it up with a proper spring for proper handling both on road and off.
Then I can simply dump the air and rely on the spring to do its job on road.

In general the only failures we had back when we were building systems were from interference issues that came with trying to fit a big ol' bag into a tiny little space.
We had some issues with line leaks but solved that forever by having a local shop crimp some ends on some braided stainless high pressure line.

Naturally I would go this route to, more or less, eliminate a failure there.
I think if the bag is up and out of harms way might work.

I planed on having an air source on board for various uses but I could put a simple Schrader valve in place so I could pump the bag up manually if the pump failed.

Also I could make the ride height such that in the even of a bag failure I could still simply run using the spring to get me home.

I still have a lot of design work left but I am not ruling anything out at this point.

 

[Sharpie]

What did you ever figure out with regards to this? I know it's been a while, but........

Thanks.

 

[dependencies]

Yes I'd be interested what happened too

 

[jerdog53]

Modern Land Rovers use air bags as their primary suspension.

 

[kojackJKU]

There was a company who acutally made a kit for JK jeeps out of airbags. It was awesome. got like 9" of additional lift out of it. really cool design too. BUT WAS SPENDY!

 

[bluejeep]

There was a company who acutally made a kit for JK jeeps out of airbags. It was awesome. got like 9" of additional lift out of it. really cool design too. BUT WAS SPENDY!

AirRock

 

[ScottReb]

Earthroamers use the Kelderman system. Seem to well liked. $6000 for parts alone so not really cheap.

 

[vwhammer]

What did you ever figure out with regards to this? I know it's been a while, but........

Thanks.

I have decided to run the bag-over-coil-over set up and I will add a couple of simple, redundant features that will get me home in the event of a failure.

I have to be very careful about my "normal" ride height selection as I am running a a radius arm system and the castor will change significantly as the suspension travels.

The arms will be similar to those on the front of an 80 series Land cruiser or front and rear on the Discovery 1 and 2

This set up is very durable and stone simple.
Not to mention it is used on most of the most capable overlanding vehicles produced in the modern era; the Land Cruiser, The Discovery and Defender and the G class Mercedes.
While these don't have Baja 1000 levels of suspension travel or rock bouncer limits of articulation, generally they are regarded as being very capable off road.
With a few select changes with some geometry it should work quite well for my particular situation.

My plan is to set it all up with a little extra positive castor when the bags are fully deflated and the vehicle is at its' lowest ride height.

The hope is that this will make it stable at speed while on road with the vehicle set at its lowest point.

Then, once the bags are aired up a bit for off road use, this should put the castor back to what would be considered stock on a land cruiser.
This would probably be the setting for most off roading.

Then there will be the max PSI setting for when I need every bit of ground clearance I can get.
Generally in this setting the vehicle will be moving very slowly and the castor angle will not be much of a concern.

I have not done any work at this point and have no plans to do so until this time next year.
However the research, design and analysis work will continue until I am comfortable that every thing will work as I see it in my head.

There will be a full build thread when work does begin or perhaps a little sooner as I finalize my drawings just to give people an idea what I am going for.

 

[spencyg]

I've been running my rig with secondary bags in the rear for years without any problem. I do carry a spare bag and spare air line and fittings in the event of failure but everything is still in great shape and I haven't had a single issue.

SG

 

[kojackJKU]

The same setup I am running, I am swapping out to new 19/60 coils as well for a bit stiffer spring as well.