Defender Airbags v coils. Final verdict

[Fraz]

Hi Forumites,

I've been doing plenty of reading on this. I've trawled the archives and also read all of these here. (http://www.aulro.com/afvb/good-oil/56981-air-bag-suspension-defender.html)

So my question is, does anyone who has converted to airbag bellows regret doing so?
If so, why?

Also, what are people's opinions about longevity with them? Has anyone ever actually experienced a blowout or show stopper off road?

I have a 130CC, I tour often over pretty arduous stuff but I am with done 'playing' in the mud. My reasons for wanting to upgrade are mainly for comfort and I love the idea of being able to lower the rear in situ. Stability and uneven loading also interests me.

I would be starting with the rear only, then if worth the difference I would convert the front at a later date.

Thanks guys

[steveG]

Definitely on my to-do list for my next project.
IIRC the only failure I recall reading of was the bag being pinched to structure somehow.
Seems like the ultimate flexibility for a variably loaded vehicle, but there doesn't seem to be much info around on suitable shocks.

Steve

[Fraz]

Should have added, I have Koni Raid HTs fitted (and very very happy with them). Being adjustable I dont see any problems re: suitability

Id be more than happy to increase the bump stops a little to rule out chassis pinching. From what I have read it would need to be done anyhow as the bags will not sit well without a spacer. This would also help minimise potential rubbing

[isuzurover]

So my question is, does anyone who has converted to airbag bellows regret doing so?


No, not for a second.



Also, what are people's opinions about longevity with them? Has anyone ever actually experienced a blowout or show stopper off road?


Mine have been in for 3 years and are still fine. That includes the canning (where we got 52 mm of rain) and several other trips including west-east-west coasts (towing).

The firestone bags are incredibly tough and very thick.

[LoveMyV8County]

Mine were good as new after 10 years (County). It'll be my top priority mod for the 300Tdi when I can find some money.

I did hear anecdotally from a 4WD accessory shop owner of a (non-LR) person who did manage to pierce one with a fence picket by recklessly driving over said fence and getting stuck. Blame the airhead not the airbag for that one though.

It's probably enough just to do the rear, you'd get most of the benefit.

Chris

[goingbush]

Ive had one let go, not in a Landy but a 1985 Lincoln Continental whilst touring USA, granted I was on a fire trail in the Appalachian mountains, These cars rarely see dirt roads, same Firestone airbag setup.

Was very disconcerting thinking I might be stuck with the tunes of Duelling Banjos in the background (if you've seen Deliverance you will know what I'm on about)

The trouble was driving out with the fuel tank banging on the ground , at least I could drive once I blocked off the compressor hose, I don't believe you can if the same thing happened in a Disco.

[bully130]

no regrets had mine in for 6 years no problems with them
done a lot of off road work with them
just fitted a air tank and in cab gauge
cheers
Ian

[Fraz]

Well now I'm bulk keen. Thanks guys :D

Ill be using Firestone bags.
My Koni shocks are not extended, so standard ride height will be fine for me. Im not prepared to change as they are brand new.

So, what bags have people used without having to change out the shockers?

From what I have read, the #5426 bags seem popular but my measurements indicate I would need longer shocks.

I cant find out what part number Firestone has written on Airbagman's kit - does anyone have this handy?

What about the controlling systems? Im good for DIY, I love it. Is it really as simple as switch, solenoid, relief valve and tube?

[roverrescue]

I was all but ready to pull the trigger on converting my 130 until one weekend a few years ago we happened along a poor stricken GU ute out near the beach at Cape Melville.

We had shot up there for a sneaky two nighter after work on Friday.

On the Saturday while going for a drive we happened along a fella with his GU ute and Ultimate.
A few kays back from the beach all jacked up with a frown on his face.
We stopped and sought how they were going.

He had firestone bags in the rear of what was an overloaded ex coil sprung GU ute.
Had blown one bag on the drive in, replaced with his spare and then blown the other side on the way out.
Trouble was the tear in both bags was right where the bag rolls onto the cone. So plug repair didnt work.
I had my tube repair kit, plenty of mushrooms repairs and a few patches and glue. We tried a few things which all failed due to the bags puncture location. That roll just loads up any repair you can think of.

He was happy and tinkering and thinking so we said we would check up on them on our way out the next morning.

Sure enough he was still stuck so we ended up towing his Ultimate out to Kalpower to take some of the load off. He ended up making the hole in the bag big enough to then squeeze in cut up pieces of all the closed cell foam mats they had. Sort of a rubbery foam spring. We went on ahead they were happy trundling at idle the couple of hundred out to Kalpower. I can only imagine they got some bags flown in to Laura and kept moving.

I guess the nature of the beast is that they can puncture / tear / bust / die.
Either carry a few spare bags or even keep your steel coil and mount plates available????

The saga turned me off the conversion because I often run at GVM in horrible country a long way from anywhere useful. I know this is kinda stupid cos I run a tdi with the rubber band, an R380 with 75% worn output splines and my front diff is standard rover fair with a zillion km and bugger all oil changes...

Anyways - just call me fickle!
I run polyairs in the coils and despite the fact they are not as good as full air springs they sag less at GVM than the OEM inner coil and ride a zillion times better.

My above ramble is just pointing out although good they are not infallible!

Steve

[goingbush]

You can always try this idea before you decide,
used to be a popular "mod" in the 1980's

https://www.aulro.com/afvb/images/imported/2013/06/226.jpg

image stolen from this post
http://www.aulro.com/afvb/technical-chatter/104339-cheap-polyairs.html

[isuzurover]

I was all but ready to pull the trigger on converting my 130 until one weekend a few years ago we happened along a poor stricken GU ute out near the beach at Cape Melville.

We had shot up there for a sneaky two nighter after work on Friday.

On the Saturday while going for a drive we happened along a fella with his GU ute and Ultimate.
A few kays back from the beach all jacked up with a frown on his face.
We stopped and sought how they were going.

He had firestone bags in the rear of what was an overloaded ex coil sprung GU ute.
Had blown one bag on the drive in, replaced with his spare and then blown the other side on the way out.
Trouble was the tear in both bags was right where the bag rolls onto the cone. So plug repair didnt work.
I had my tube repair kit, plenty of mushrooms repairs and a few patches and glue. We tried a few things which all failed due to the bags puncture location. That roll just loads up any repair you can think of.

He was happy and tinkering and thinking so we said we would check up on them on our way out the next morning.

Sure enough he was still stuck so we ended up towing his Ultimate out to Kalpower to take some of the load off. He ended up making the hole in the bag big enough to then squeeze in cut up pieces of all the closed cell foam mats they had. Sort of a rubbery foam spring. We went on ahead they were happy trundling at idle the couple of hundred out to Kalpower. I can only imagine they got some bags flown in to Laura and kept moving.

I guess the nature of the beast is that they can puncture / tear / bust / die.
Either carry a few spare bags or even keep your steel coil and mount plates available????

The saga turned me off the conversion because I often run at GVM in horrible country a long way from anywhere useful. I know this is kinda stupid cos I run a tdi with the rubber band, an R380 with 75% worn output splines and my front diff is standard rover fair with a zillion km and bugger all oil changes...

Anyways - just call me fickle!
I run polyairs in the coils and despite the fact they are not as good as full air springs they sag less at GVM than the OEM inner coil and ride a zillion times better.

My above ramble is just pointing out although good they are not infallible!

Steve

Nothing is infallible - just like the Pajero at well 28 on the canning with two broken coils...

What age were the bags? What diameter (approx) and what shape piston?

[roverrescue]

I vaguely remember running it past you at the time Ben:
-Essentially new bags (well as long as it takes to drive from Victoria to this neck of the big bad woods)
-Diameter was 10 ish inches they had been fitted by a real proper en-gin-eeeer and everything!
-piston was lightly tapered as per most fender fit outs I have seen.

All in all it looked like any air fit out I have seen on AULRO
He carried a spare bag which essentially got him an extra 50km ;)

I can only imagine the issue was the stupidly heavy load he carried
Tray was fully enclosed with draws and cupboards and crap and crap and crap and crap
4.2m tinnie on the roof and 25 horses of yammies finest in the canopy

I shudder to think what it all weighed. I would guess his canopy weighted more than my entire defender. And then with the Ultimate 150kg of draw bat weight I can only imagine them bags were working hard!



We have had a front coil break on a mates GU up on the coast north of the Mitchell Plateau.
It collapsed down on itself, a few hose clamps were attached to make it look like we had performed a repair and we drove it out to Kunnas. Ill take a busted coil over a busted air spring any day!

[isuzurover]

I vaguely remember running it past you at the time Ben:
-Essentially new bags (well as long as it takes to drive from Victoria to this neck of the big bad woods)
-Diameter was 10 ish inches they had been fitted by a real proper en-gin-eeeer and everything!
-piston was lightly tapered as per most fender fit outs I have seen.

All in all it looked like any air fit out I have seen on AULRO
He carried a spare bag which essentially got him an extra 50km ;)

I can only imagine the issue was the stupidly heavy load he carried
Tray was fully enclosed with draws and cupboards and crap and crap and crap and crap
4.2m tinnie on the roof and 25 horses of yammies finest in the canopy

I shudder to think what it all weighed. I would guess his canopy weighted more than my entire defender. And then with the Ultimate 150kg of draw bat weight I can only imagine them bags were working hard!



We have had a front coil break on a mates GU up on the coast north of the Mitchell Plateau.
It collapsed down on itself, a few hose clamps were attached to make it look like we had performed a repair and we drove it out to Kunnas. Ill take a busted coil over a busted air spring any day!

Weight doesn't seem to make sense. I saw a full size dump truck in kunners running the same air springs as me! (admittedly 2 pairs per axle).

The broken coils I mentioned were in 3+ pieces per spring. Well beyond hose clamps.

[Albert]

After going through the Simpson I intalled bags, (I will try to post part numbers later)
I am taking them up the Canning next week so I hope they go ok. I am now packed up ready to go but she still rides like a pogo stick, running 70 PSI. I can only put it down to shocks.
I bought the air bag man kit with in cab controls and 2 1/2g tank. A bit surprised the tank doesnt have a drain port or pressure relife valve. If I did it again I would go with a Air On Board tank. They also do control valves but Im not sure about duel needle gauge.
I had trouble with my older ARB pump, it was melting the solder in the glass fuses and the plastic on the blade fuses without blowing them. It ended up shorting out when the plug melted. Not up for 2.5 gallons at 100psi.:(
So at short notice I got a TJM pump, was great untill I tried to mount it. The inlet and pressure ports are BSP, but the outlet is a nitto fitting with a thread no fluid power shop could identify! and because of the direction it came out it wouldnt mount under the drivers seat where I wanted it. :censored: It has turned into a nephews birthday present
Coming really soon is a Air On Board pump has 100% duty at 100psi. Will have to leave a day later so I can fit it. Nothing like leaving it to the last minute

[130man]

Hi Fraz. I have replaced the rear coils on my TD5 130 extra cab with the Firestone air bags following TimNZ's excellent tutorial. This occurred in September 2012, so I have not done a lot of kms with them yet. They are marvellous as they allow me to run empty with a decent ride and then load up with a Trayon camper and all the gear and still get the same ride/ clearance. I do notice the shockers top out now and then on the larger bumps at road speeds, so I will need to replace the shockers with longer travel ones soon. My system is very basic , with a Schrader valve for each airbag located nearby . It means I have to adjust the pressures individually but it doesn't take long. Being able to lower the suspension and drive out from under the camper is worth it all by itself. Cheers, 130man.

[frantic]

There are 2 fully bagged defs that I've seen. One is the 130 of cal who also is building a stunning county with a Chevy block and another is owned by a Sydney opposite lock, store owner who has a fully kitted def 110 wagon. Sorry cannot remember which store but it is at the 4wd expo the last few year's.

[ozscott]

How do they go for legalities. I thought in qld at least it was engineers certification or no go.

Cheers

[rick130]

I don't think anyone would have stressed them anymore than Tony/Rangierover in his 120.
It's his farm hack, do anything, load anything in any conditions vehicle.

How is it going ?

[rick130]

How do they go for legalities. I thought in qld at least it was engineers certification or no go.

Cheers


I'm guessing an Airbag Man kit is pre-approved, DIY I'd just do it anyway, but that's just me.

[Dougal]

So what about control systems and balancing pressure each side?

Do you guys just pump them up until height looks right and use front coils to judge when each side is even? Anyone trying to cross-link them or not enough remaining roll-stiffness?

I took my EAS rangie for it's possibly first ever offroad jaunt on the weekend. I'm starting to really really like air suspension.

[rovercare]

So what about control systems and balancing pressure each side?

Do you guys just pump them up until height looks right and use front coils to judge when each side is even? Anyone trying to cross-link them or not enough remaining roll-stiffness?

I took my EAS rangie for it's possibly first ever offroad jaunt on the weekend. I'm starting to really really like air suspension.

Cross linking? Big no no, think about it

Pressure is not a great judge with air, actual height is, accuair is about the best controller, or was when I installed

[Dougal]

Cross linking? Big no no, think about it

It's no problem at all provided you've got the roll-stiffness elsewhere. L322 and later vehicles all do it.

[rovercare]

It's no problem at all provided you've got the roll-stiffness elsewhere. L322 and later vehicles all do it.

On a live axle? Apples and oranges

It works well offroad, not on road

[Dougal]

It works well offroad, not on road

Well yeah. I thought that was obvious enough to not mention. A valve on the cross-link line is on all the factory setups.

[rovercare]

Well yeah. I thought that was obvious enough to not mention. A valve on the cross-link line is on all the factory setups.

Is it on you classic? how about P38? how about any factory live axle setup?

Apples and oranges

[Dougal]

Is it on you classic? how about P38? how about any factory live axle setup?

Apples and oranges

Classic and P38 don't have any off-road cross-linking (no off-road mode to trigger it I guess). But they do apparently bridge the front bags to equalize pressure in some situations.

The progressive nature of the air bags gives them a lot of roll-stiffness. With the EAS computer unpowered jacking one corner of the EAS classic gives a lot less articulation than the coil classic. But offroad it seems to have no problems keeping wheels in contact.

Others have cross-linked P38's. I'll give it a shot on the classic when I get my manual inflation lines hooked up.

[TonyC]

Snip...

Anyone trying to cross-link them or not enough remaining roll-stiffness?

Snip...

I asked this question in another thread, the one on Tony/Rangierover 120, I think.

Tony was using air springs and a X Eng Disconnect sway bar (which he broke) I asked if a better way way might be to have a fixed sway bay and cross link the air springs (off road), but it got lost in the chatter, I think.



How do they go for legalities. I thought in qld at least it was engineers certification or no go.

Cheers

In Vic converting from coils to air require engineering certification, as Rick said I don't know if the Airbag Man kit has some sort of type approval.

Tony

[rovercare]

I asked this question in another thread, the one on Tony/Rangierover 120, I think.

Tony was using air springs and a X Eng Disconnect sway bar (which he broke) I asked if a better way way might be to have a fixed sway bay and cross link the air springs (off road), but it got lost in the chatter, I think.




In Vic converting from coils to air require engineering certification, as Rick said I don't know if the Airbag Man kit has some sort of type approval.

Tony

The sway bar got damaged due to the extension we put on the mounts, tony copied mine and got the same flaw, mine also bent

Cross link works in offroad, kinda, you can only do one end, a mates tray had bagged rear and solenoid to crosslink, in the end though it was not worth it, to tippy, your better off forced articulation, ideally a pendulum and good control will be the go

Anyhow, at dougals rate it will be 2056 before he tries anything:D

[Dougal]

Cross link works in offroad, kinda, you can only do one end, a mates tray had bagged rear and solenoid to crosslink, in the end though it was not worth it, to tippy, your better off forced articulation, ideally a pendulum and good control will be the go

Sproklegrommet - Self Leveling DIY Air Suspension (http://www.x-eng.co.uk/Sproklegrommet/LRSuspension/Index.asp)

Anyhow, at dougals rate it will be 2056 before he tries anything:D[/QUOTE]

2020 easily. I don't apologise for having a life competing for my time and money outside rovers.

[flagg]

Sproklegrommet - Self Leveling DIY Air Suspension (http://www.x-eng.co.uk/Sproklegrommet/LRSuspension/Index.asp)

Anyhow, at dougals rate it will be 2056 before he tries anything:D

2020 easily. I don't apologise for having a life competing for my time and money outside rovers.[/QUOTE]

Haha rub it in why don't you :p

Seriously though, I change my mind ever other week about air suspension. Simplicity vs comfort. I'll end up doing it eventually, and that Nissan is the only bad word I've heard... But overloading will kill everything, so it seems kind of moot.

When I get a decent tube bender Ill make up some safari style front shock mounts and start from there, but I would like to keep my swap bar. (Rear locker so huge articulation less critical).

[Bush65]

The pressure resulting in air springs when they are compressed or extended depends greatly up where the static ride height was, and the air pressure at static height.

When an air spring is anywhere close to full extension, they don't like much pressure. With no cross linking that problem won't occur, because the pressure drops as the trapped volume increases during extension.

The issue with cross linking is the the compressed side air spring increases the pressure in the extended side air spring. That would be ok for limited axle articulation but bad for the life of the bellows for large articulation. IMHO don't do this.

Forced articulation (linking front and rear) would be good, but simple ways of doing it are difficult when payload is so variable.

[rovercare]

Sproklegrommet - Self Leveling DIY Air Suspension (http://www.x-eng.co.uk/Sproklegrommet/LRSuspension/Index.asp)

Anyhow, at dougals rate it will be 2056 before he tries anything:D

2020 easily. I don't apologise for having a life competing for my time and money outside rovers.[/QUOTE]

Dreams are cheap:p

I'm not all that clever, but I've actually tried most these ideas in the real world

[Bush65]

I don't think anyone would have stressed them anymore than Tony/Rangierover in his 120.
It's his farm hack, do anything, load anything in any conditions vehicle.

How is it going ?
IIRC Tony had a bellows fail due, it appears, to being pinched between the spring perch on the chassis and the bottom plate of the airbagman spacer.

I suspect (from seeing the photos) two issues with how the air spring was mounted that contributed to the failure:

(1) the design of the spacer is not good IMHO. Its width is approximately equal to the diameter of the end closure crimped to the bellows, which leave a gap between it and the spring perch where the bellows was being forced when the air spring was fully compressed (axle on bump stop).

(2) the edges of the plate were not rounded off, leaving an edge that wore the bellows. IMHO the plate should extended right across the inside of the perch so there are no gaps or edges to abrade/pinch the bellows, just a flat surface to roll on.

Firestone recommend a minimum pressure when the air spring is fully compressed, and I do wonder if all of the air may have been dumped when the airsprings were lowered to the bump stops.

[Dougal]

The pressure resulting in air springs when they are compressed or extended depends greatly up where the static ride height was, and the air pressure at static height.

When an air spring is anywhere close to full extension, they don't like much pressure. With no cross linking that problem won't occur, because the pressure drops as the trapped volume increases during extension.

The issue with cross linking is the the compressed side air spring increases the pressure in the extended side air spring. That would be ok for limited axle articulation but bad for the life of the bellows for large articulation. IMHO don't do this.

Forced articulation (linking front and rear) would be good, but simple ways of doing it are difficult when payload is so variable.

The main point, being don't fully extend or pressurise your bags at full suspension travel.

Interestingly the stock RRC bags only have ~165mm of stroke between fully seated and bulged (vehicle on bump-stops, level ground) and fully extended (vehicle on trolley jack, wheels in the air). At high ride height it sits level 45mm below full extension and 120mm off the bump-stops.
P38 bags are allegedly shorter again.
The L322 has something like 11 inches of front suspension travel and more in the rear.

The challenge is to fit longer bags without them fouling anything else.

[Fraz]

Thanks everyone for the feedback.

So this is a go ahead for me - I am only doubting the controlling system now.

Ive had a few quotes returned to me and to say that Im not very impressed with figures is an understatement.

Saying that though, Airbagman's level of knowledge shown, along with the very personalised email was pretty satisfying. Im not quite ready to outlay the $ yet, at least until I know how I will control it.

AccuAir's e-level system was mentioned in one quote. Does anyone have anything to say about it?

[Albert]

Part numbers for Air Bagman AB0051.
Firestone part number: W01-358-5422
I would look at Air On board for tank and pump and control valves. at least their tank has a drain port on it.

[Bush65]

Albert posted that Airbagman use Firestone W01-358-5422 air springs. So I pasted some comparisons from a catalogue - first pic.

The top air spring shows some details for the W01-358-5422. It uses a 1T14C-3 bellows with an internal bump stop, and a 3.62" high piston. IMHO this is a good candidate for the rear of a Defender.

The next air spring uses a 1T14C-7 bellows without internal bump stop, and the same piston. Note the difference in max height is 4" = 7" - 3" (see where -3 and -7 are in the bellows number). Also note the difference in minimum height, due to the internal bump stop. For our vehicles, you should use the external bump stop and not rely on the internal. For no internal bump stop, the external bump stop should be set to limit the minimum height similar to if it had an internal bump stop.

The last air spring is what a few members have used with success. The difference in maximum height is due to the -7 bellows and a taller piston. The difference in minimum height is due to the taller piston.

All 1T14C-? bellows are similar apart from height (the -? part). Internal bump stops and differences in the closure plate at the top, which were changes made to suit different customer's installations (these are replacement air springs for OEM's). The -? can be -1, -3, -5, -7, -8. IIRC, one member here, cal415, is using -8 bellows in the rear of his 130.

The next 2 pics show the problem Tony had with the bellows pinching at the top.

The last pic relates to my earlier post about not to cross link air springs, it is the data sheet for an air spring with the 1T14C-7 bellows and 3.82" high piston. The shaded area on the left, from 17.4" to 20" is marked do not use in this area without consulting Firestone Engineers (or such like). At these extensions Firestone recommend very low loads on the air spring, and hence low air pressure. In this range the bellows is unrolled or close to unrolling from the piston and the effective area is diminishing quickly. The air springs that Land Rover use in RRC and P38 are a different style and construction to these Firestone air springs.

[Dougal]

Thanks John.
So next question.

At full axle articulation, how much spare capacity do you need in the bag over the same length on a completely straight extension to account for the angle of the axle?

Is it enough to make sure the longest diagonal doesn't exceed the normal max length?

[yt110]

[QUOTE=Bush65;1938321]Albert posted that Airbagman use Firestone W01-358-5422 air springs. So I pasted some comparisons from a catalogue - first pic.

The top air spring shows some details for the W01-358-5422. It uses a 1T14C-3 bellows with an internal bump stop, and a 3.62" high piston. IMHO this is a good candidate for the rear of a Defender.


These are the ones I have,I got the airbagman kit and onboard control kit.

The kit also came with 25mm spacers for the external bump stops.

The backup and support from the Airbagman was fantastic.

The posts by Bush 65 on Chooks Defender 110 regarding rear suspension heights helped solve my initial handling problems(I was setting the rear ride height too high)

Jim.

[Albert]

The other big question is what shocks should I be using?
I have a set that came with the 86 county, +2" dobinsons. I have a fair amount of wieght onboard and it has a fair bit of wallowing and a good dip will keep it bouncing a few times. Not bad but I think it should be better with stiffer shocks?
Any thoughts

[BilboBoggles]

I want to do this, but I'm worried about roadworthiness rules and insurance. In Victoria would you need engineers certificates?

[flagg]

I want to do this, but I'm worried about roadworthiness rules and insurance. In Victoria would you need engineers certificates?

I'd say yes, but contact VicRoads to be sure. If they say no, get it in writing and keep it with you in the car incase plod disagree.

[TonyC]

I want to do this, but I'm worried about roadworthiness rules and insurance. In Victoria would you need engineers certificates?

Yes engineering is needed. See section 13.6 in this document on the Vicroads website.

http://www.vicroads.vic.gov.au/NR/rdonlyres/9B3A858D-15A0-4572-90BF-3D08214BF7BE/0/VSInumber8Guidetomodificationsformotorvehicles.pdf

Tony

[BilboBoggles]

Last time I looked into an Engineer certificate was for a single bolt for a child restraint, and that was could to cost several hundred dollars. I would guess that such an extensive mod is going to cost a fortune to certify. Has anyone done this?

Are there any companies offering a certified conversion kit in Victoria?

[Albert]

Last time I looked into an Engineer certificate was for a single bolt for a child restraint, and that was could to cost several hundred dollars. I would guess that such an extensive mod is going to cost a fortune to certify. Has anyone done this?

Are there any companies offering a certified conversion kit in Victoria?

Give Air bag man a ring. I asked them about this when I bought mine. I assume they are certifide in Vic as well, but they will soon set you strait.
Fitted my Air On Board pump today, much more confident in the system now. still a few bits to fix up but that can wait till I get back.

[Ranga]

Give Air bag man a ring. I asked them about this when I bought mine. I assume they are certifide in Vic as well, but they will soon set you strait.
Fitted my Air On Board pump today, much more confident in the system now. still a few bits to fix up but that can wait till I get back.

So, what's the story re: engineering certificate for QLD?

[Dougal]

So getting back to this cross-linking. It appears the classics and P38's do it on the front bags.

According to the official literature, When initially moving off and then every time the speed drops to nothing, the front bags valves are opened to allow the pressure to equalize between the two front bags.

So. In an offroad situation, continuing to move will make them keep operating as independent springs. But stop (for example being cross-axled) and the valves will open to allow the pressures to equalise and the bags to cross-link. Letting the high side compress and the low side extend more than they would.
This makes perfect sense, because otherwise the combination of the large front sway bar and highly progressive air springs would prevent these vehicles ever getting through a marginal cross-axle situation.

I am not sure at what or any point the self-levelling then takes back over. The side-side levelling of classics and P38's is done solely on the rear bags, but the height of the fronts is read for levelling purposes where the lowest height is used. If the front bit counts are set wrong, the ECU on mine spends a bit of time shuffling air in and out to find a suitable height. There is I think a 2 bit window for the dead-zone where it deems the height to be correct.
Setting the front height sensor bits unevenly results in more valve activity, but it still levels out.

[Bush65]

IIRC the air springs used in RRC and P38's were of a different style to the Firestone 1T style air springs. I can only guess why Firestone caution against carrying load over when the 1T air springs are near full stroke.

Firestone provide a design manual for using their air springs for suspension, which they refer to as 'airide' and a separate manual for actuators and vibration isolators ('airstroke' and 'airmount'). The data sheet I posted earlier was from the airstroke and airmount manual, but a good deal of it is relevant to the same air spring when used for suspension. Unfortunately the airide manual only includes one data sheet for illustration. Airide data sheets have more information that is useful for suspension design, but much of that can be calculated from the static data provided in airstroke/airmount data sheets (see my spreadsheet for springs that I have posted elsewhere on aulro).

When the 1T style air spring extends beyond the height where the bellows begins to roll off the piston, the effective area reduces at a rapid rate. This can be seen on the constant pressure curves for load vs length, where even at 100 psi, the load is small at maximum extension.

This, I guess, is the crux of why Firestone say not to carry load at those lengths - as the sustained periods of the high pressure required, combined with a stretched bellows, leads to failure of the bellows near the bead where the end closure is crimped on. Another issue would be the additional increase in pressure of the trapped air as the air spring is compressed from near it's maximum height.

However it may also result in the bellows not rolling back onto the piston properly as it is compressed from maximum extension under load.

With a manual control system for ride height, unless limit straps or shockies were set-up to limit maximum extension, it would be possible to inadvertently raise the air spring too far under high load - user beware!

Edit: this pic is the air springs I fitted to my rangie many years ago. They had a useable height range from 7" to 20". From the one on the right you can see how the effective area reduces when the bellows is no longer rolling on the piston.

[Dougal]

Here are some pics from my RRC with factory EAS.
It only has ~165mm of stroke. From the bumpstops low ride height is +60mm, std height is +80mm, hi position is +120 and max height is ~165mm.

Old bags vs new bags:
The old bag is a front which is supposed to be 350mm long when new. The replacement is a rear bag which is 360mm long as shown.
https://www.aulro.com/afvb/

Old bag at Hi Position Left Front. This one was leaking.
https://www.aulro.com/afvb/[/B]

Other side at Max extension (this is ~45mm higher than the offroad hi position should be. But at this point my heights were a bit screwy).
https://www.aulro.com/afvb/

Close up same position:
https://www.aulro.com/afvb/

New bag installed and on the bumpstops, this is a 360mm rear bag installed on the front:
https://www.aulro.com/afvb/

Same bag at the offroad high position.
https://www.aulro.com/afvb/

[Fraz]

I have written to RMS or RTA or whatever they are called this week requesting direction to the legislation regarding a conversion. I understand it will need to be engineered, but the only problem they have with it is in the way the controller behaves.

From what I understand, the controller is supposed to:
-prevent the driver making adjustments while the vehicle is moving
-have some sort of mechanism in place to respond to a catastrophic blowout

I see no logic in paying $1500+ for a controller when I can get the bags for $150 each

I will post what they respond with for others

[ozscott]

Never used to be legal in Qld without engineering certification. ..cant immagine its changed. I can buy a HID kit for my D2 but its not kegal to fit. Ie just cause its a kit sold for a particular vehicle doesnt make it legal and not in each state.

Cheers

[airbagman]

Hi, from Airbag Man.
At present on WA has clear rules about the fitment of air springs as a bolt in replacement for coils on a 4x4 vehicle, VIC, NSW and QLD are all in the process of writing or looking at new rules to cover this. We are working with the various authorities to assist them through this process, and it will take some time. In QLD and NSW you can make an individual submission for approval, however there is no direct ruling requiring this, and in VIC their rule 13.6 was written mainly to cover low height vehicles with air front and rear and chassis modifications, so we are working on figuring out a way to get bolt in kits passed via an easier channel. If anyone is looking at doing a conversion we suggest that you give us a call to check our progress in your state.
As a side note, we have done a lot of with with cross linking and custom airbag arrangements on Defenders so can advise on alternatives to our standard kits.

[isuzurover]

WA rules for anyone interested.
http://www.transport.wa.gov.au/mediaFiles/LBU_VS_IB_126.pdf

[steveG]

Hi, from Airbag Man.
At present on WA has clear rules about the fitment of air springs as a bolt in replacement for coils on a 4x4 vehicle, VIC, NSW and QLD are all in the process of writing or looking at new rules to cover this. We are working with the various authorities to assist them through this process, and it will take some time. In QLD and NSW you can make an individual submission for approval, however there is no direct ruling requiring this, and in VIC their rule 13.6 was written mainly to cover low height vehicles with air front and rear and chassis modifications, so we are working on figuring out a way to get bolt in kits passed via an easier channel. If anyone is looking at doing a conversion we suggest that you give us a call to check our progress in your state.
As a side note, we have done a lot of with with cross linking and custom airbag arrangements on Defenders so can advise on alternatives to our standard kits.

Great that you're actively working on this, and its a much more realistic position that you had a few weeks ago when I asked regarding certification in Victoria.

Steve

[flagg]

In QLD and NSW you can make an individual submission for approval, however there is no direct ruling requiring this,
.

Thanks. Are you referring to the standard process of engineering sign off or something else?

[flagg]

WA rules for anyone interested.
http://www.transport.wa.gov.au/mediaFiles/LBU_VS_IB_126.pdf

That all seems pretty sensible.. I hope the other states follow soon.

[Bush65]

I have written to RMS or RTA or whatever they are called this week requesting direction to the legislation regarding a conversion. I understand it will need to be engineered, but the only problem they have with it is in the way the controller behaves.

From what I understand, the controller is supposed to:
-prevent the driver making adjustments while the vehicle is moving
-have some sort of mechanism in place to respond to a catastrophic blowout

I see no logic in paying $1500+ for a controller when I can get the bags for $150 each

I will post what they respond with for others
for those two requirements, I see no reason why what others like Isuzurover have done, would not satisfy them.

The first one is obviously met, with external inflation of individual air springs.

With the second requirement, in a Defender with 110" or 127" wheel base, and rear air springs, at stock ride height, there will be little drama if one air spring suddenly deflates. That side will drop the small distance to the bump stop, and the other side will also drop a little as more load is transferred to the good air spring.

With the suspension at stock height and lower, the roll steer is not significant.

Just my opinion.

[Albert]

I can say that with a blow out on rough roads you are right. No worse than a tyre going POP!
Wished I had carried a spare :(

With the second requirement, in a Defender with 110" or 127" wheel base, and rear air springs, at stock ride height, there will be little drama if one air spring suddenly deflates. That side will drop the small distance to the bump stop, and the other side will also drop a little as more load is transferred to the good air spring.

With the suspension at stock height and lower, the roll steer is not significant.

Just my opinion.

[TonyC]

I can say that with a blow out on rough roads you are right. No worse than a tyre going POP!
Wished I had carried a spare :(

Hi Albert,
What air spring were you running? and what do you think caused it to fail?

Thanks

Tony

[Albert]

Hi Albert,
What air spring were you running? and what do you think caused it to fail?

Thanks

Tony

Airbagman kit, firestones.
Cause was mine, not really suited to army chassies.
I saw some rubbing marks and thought a bit of plastic would help...bad idea, acted like sandpaper
That was on after the Heather, Gunnbarrel, and Canning carrying a full load over six weeks. I would get them again if I get a standard chassie.

[rar110]

Airbagman kit, firestones.
Cause was mine, not really suited to army chassies.
I saw some rubbing marks and thought a bit of plastic would help...bad idea, acted like sandpaper
That was on after the Heather, Gunnbarrel, and Canning carrying a full load over six weeks. I would get them again if I get a standard chassie.

So Albert does the chassis have the extra flange/flat to help retain the top of the spring?

That might rule out air springs for me too.

[Albert]

So Albert does the chassis have the extra flange/flat to help retain the top of the spring?

That might rule out air springs for me too.

The peice of flat did rub, but thats not a problem, it can be bent out a bit or cut off.
The problem is the box section chassie mod that attaches behind the spring mount/ outrigger. The angled support bracket is a lot closer at the rear compared to the front one. I dont have a pic of it here but i will try to post one tonight or tommorow night.

[Albert]

64187
As you can see on the rear side, thereis not the 1" clearance reccomended.
This didnt wear much.... untill I put a piece of plastic there to stop the rubbing;)
Love the airbags. Great for the rear camper. When stopped on uneven ground I could just adjust each side to level it up.