Air Springs

Hi. For a start you don't replace the coil springs with the air bags, the air bags the coil springs and if you are expecting instant inflation and deflation forget that too as the airbags are fed through a 1/4" hose.
The idea of airbags is to level the vehicle when loaded and to give a softer ride. Try looking at :- trucksprings.com they can supply you with airbags, compressors and all the fittings plus a technical back up for what you need.

If you can view the Patrol site there is a current thread in the GU section talking about them. While you may not be able to post at least you should be a able to read it.

Hi Nic,
I posted a similar question here a couple of weeks ago thread named "probags". I got a similar result that "bags don't replace springs". There are some that do, Probags being one of them (no connection). The impression I get is that you just adjust height for the terrain and leave it at that. They don't continually adjust,
the air is for that. You can connect them left to right for extra articulation but needs to be valved so this is not the case for normal driving. I am yet to clarify what is done about castor adjustment but as I'm doing most of my driving at normal height I'm not too concerned about it.
So in short adjust bags for load and raise if needed for clearance and that's about it, seems like a good system to me. Camber would need to be sorted if you drive with them continually raised,brake lines could be an issue too.
There was an article in 4wd monthly some time back but would have to dig.
hope this helps
Paul
The compressor is there just for convenience and they can be inflated before the tough terrain.

As we have just nursed a cruiser out of the northern Simpson after its airbags broke my advice would be to stick with the coils for durability.
The mounts that are provided to mount the airbag to the chassi and diff housing are rubbish and are not suited to off road conditions.
Ride is compromised in rough terrain (too stiff) as the bags need to be inflated to carry the weight reducing articlualtion and increasing shock loads to vehicle and running gear, never mind the passengers.
They might be fine for smooth road use but not up to the job on dirt and across country.
Interestingly too when talking to repairers in remote towns like Birdsville and Oodnadatta they say that airbags are the cause of a lot of breakages and tyre damage on rough terrain/roads.

Nic,

I have the Probag system in my Patrol Dual Cab Conversion and am very happy with the performance all round. I have had some self inflicted problems with them that an experienced installer probably would not have but I put the system in myself so I would know the way it worked should I encounter problems.
My bags inflate independently of each other and it's set and forget with pressure depending on load. I cannot agree with most of the issues highlighted in the thread above as problems but there are a number of different types of bags so I can only comment on the probag triple convoluted + Koni set-up that I have.

AFAIK there are no negatives performance wise, only pluses. Ride is smooth and controlled under all circumstances. As a word of caution, no matter which type you choose you must test at max load and full articulation on either side that nothing will snag the bags or rub on them at all. AMHIK!

OT

OT

Hi Nic I,
I have had the firestone air springs in the rear for about 3 months.The type of work i do it is ideal sometimes 600-700K of steel then nothing at all.I also use it for a steel camper that goes on the back.I have done a few nsw touring trips which it all worked fine after you get the right pressure settings.I have installed now a wireless remote control which i adjust the pressures L/R separate or together,I find i adjust it alot having that system.(separate compressor with a manifold matched to remote control,AIR LIFT PRODUCT
I find that you do get a bit of the swaying which doesn't take long to get use to it
Before i installed the bags i strengthened the top towers with side plates on the chassis with RHS in between to stop cracking.
I will be able to give you a good report shortly as we are heading off to the kimberley for a 4week round trip in 2 weeks time.2 utes set up the same way with air springs and edelbrock shocks .I haven't weighed mine but the other ute came at 3.6T.

Nic1
sort out th replies, there are replacement bags and there are assister bags...if an assister bag goes bust, your in trouble, they hinder articulation etc...but u and i are not talking about in coil assister bags...they are on ebay for $575 a pair and look the goods....but be careful to factor in an engineers report and possible problems with insurance.
Andrew

Thanks all for your replies, which are most helpful and appreciated.

However, I'm still missing information about how you use these air springs (let's call them air springs to avoid confusion with air bags, bellows, helpers etc, which are NOT what I'm trying to find out about), and how reliable and suitable they are for rough offroad conditions.

Firstly, please don't get me wrong - if they are reliable and do the job I want from them, air springs would be perfect for my purposes of big load/no load, loading/unloading the heavy camper, and the combination of tar and varying dirt conditions I'll be encountering.

Here are my guesses: On the tar you would have the rig as LOW at both ends as you could get away with for load/clearance, to improve centre of gravity and handling.

However, on the dirt you'd RAISE pressures and therefore clearance to match the track conditions, and at the extreme end of this range (high-clearance, very uneven/rutted tracks) potentially causing the articulation speed/responsiveness problem I'm concerned about.

Cheers,

Nic

I've just heard from a 4wd suspension outfit in Melbourne that truck drivers and road authorities have found that trucks with air spring suspension have much worse ride and bigger road impact over corrugations and other rough surfaces, than those with conventional springs.

This supports the theory that when air springs have enough air in them to match loads/clearance requirements they become very stiff and non-conforming, or at least aren't able to react quickly enough to the changes in surface.

I know trucks aren't 4wd's, but perhaps the same principles apply ?

Just read your comments above Nic but my first thought was to sugges you look to the 4x4s that require the fastest response in their suspensions - the competition cars.

Just look at which ones have air suspensions of the comp cars. None of them, I would venture to say, even though you may say the pressures are infinitely variable and thence the rebound rate

It doesn't work that well Nic as deflection force across an air spring is not as linear as a coil spring.
Great for assitance though.

Its quieter these days but I still moderate the original Patrol group
http://autos.groups.yahoo.com/group/Patrol4WD/

And it can be joined.