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Discussion Starter · #1 ·
Hey everyone,
I know there are quite a few previous posts about the subject but every post i read seems to have a different setup..
so im changing my rear springs to the full coil replacements (firestone) , what bags is everyone running...?? i have heard from 5429's to the airbag man supplied 5422's also 5712's which dont have an internal bump stop.
Im looking to stay around the 3" mark as this is the same as my current setup, i have procomp remote res adjustable shocks with 11" travel.. and will be fabricating my own mounting brackets to adapt to diff and chassis.
any information would be greatly appreciated..
 

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Discussion Starter · #3 ·
Best recommendation is for the 5429. Better than 5422 in my experience.
Thanks GQshayne, you have popped up several times on the threads I have read.. you must have good experience with the airspring system.. I forgot to mention mine is for a Ute but I wouldn’t think it would matter much..
 

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Hi Mitcht_21,
I have also been running the full airbag suspension for quite a few years on my GU Wagon front and rear. Started with an Airbag Man kit front and rear but quickly found a few limitations with their standard set up. I think their top brackets are OK bit the bottom bracket in their kit wer horrible. They had tried to design to fit standard height no lift sspension and had consequently tilted the spring base forward at an awkward angle. Then their raised height kit used that same bracket which sat at abad angle for the raised spring and worst is that iff the spring did come up all the way to hit the internal bump stop, the angle made the stop hit off centre and could do internal damage to the airbag bladder. I will put up a photo later to show what I mean there.

These are my current air bag set up front and rear both use the same Firestone Bag for ease of supply and repair or replacement if needed when travelling remote areas. But since I have made changes to the initial AirBag man kit I have not had a leak or rub issue in the last nine years. Both pairs of bags I have changed to new after 9 years which is not bad going compared to tyres and othe rubber components. So as far as reliabiliyt and punctures I think that should shut up the people that say they will get a hole and you get stuck in the bush. If they are set up well they are great.

My front and rear shocks are KONI 90, 4" lift front and 2" lift rear which both end up to be about 9" travel length. I wanted to have easy to get air bags so stayed with ones from Firestone AirBag Man list. They tried to talk me into a shorter bag but it really didnt work well at all. You can see in my photos that the airbags are right on their maximum streatch limit at full shock travel which is not really ideal. I would rather an airbag that was 1" or 2" longer than I have, but ther wasn't much in between these 5412 and the much longer 5429.

So if you have 11" travel shocks you are better off going the longer airbag to start with.



534246


Front mount uses the AirBag Man top and bottom, which are not perfect but do work well being simple. The bottom uses the tapered or flared out piston shape which I think improves the ride in the middle part of the height range but makes it very hard if I were to lift it up higher. Air bags have a sweet spot ride range in the middle of their extension, they do not work well over the whole height. But a longer bag length tends to have a longer sweet spot as there is more bag length in that middle range. So a short bag has a short ride height adjustment where it is nice, compared to a longer bag which might ride wel through a much longer adjustment height range. The only down side of the longer bag is having more of the bag bellows that you have to design to not have anything around it rub on the extra wall length as it folds down so much more when compressed.



534247


Rear bag uses the same 5412 as the front with the piston that comes with the bag rather than the Air Bag Man lower tapered out piston. I have cut the diff spring seat off, moved it forward, had a heavier duty base welded on the diff and tilted the angle around the diff slightly to get better angle. Its also critical that on full compression to the bump stop that the bag hits dead centre on the upper mount so the internal bump stop doesnt cause damage to pinch the bag.

I have done these with first getting the diff alignment and pinion angle correct for the intended ride height on mine is good at about 2.5" to 3". Diff pinion angle is adjusted rolled forward down at the front slightly to bring it to parallel to the with the gearbox output flange, using slightly longer lower arms (I think they were 10mm or 15mm from memory) then adjustable upper arms which are adjusted shorter to roll the diff forward.

5412 bags that I use:

534250


5429 bags are quite abit longer but needed if you go for 11" shock travel. Note the different base mount that you will need to work out a bolt on base for.

534251



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Here is the original AirBag Man lower rear base at full shock drop. It was just crap angles for 2' or 3" lift height. The diff sat wrong angle to compensate and the bag did not hit central on the bump stop when the diff came all the way up. You can see my shocks were too long for the airbag that AirBag Man recommended for 2" lift. It just didn't work well. Below is a cut away of the air bag bump stop and top section were hitting off centre, damaging the bump stop a bit. This one was not too bad but one bag the bump stop hit so far off that it pinched the top side of the bag against the spring mounting causing a leak.

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This was me setting up the angles for the new airbag mount and diff pinion angle correction to get it to line up and hit as close to central on the top mount. Your main chassis bump stops should probably stop it from ever fully bottoming out like that but I figured that after one leak, I wnted it to be idiot proof this time.
 

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Brackets
This is the rear lower bracket that a local welder friend in Perth came up with. It has the lower loop moved forward on the diff to line up as the diff comes up to bump stop and correct for adjusted pinion flange angle for the ride height.

There are two options so I could still put the springs back on their original plate base if I ever needed to go back to springs. Then a solid round plate for the airbag base to bolt to. My airbag base uses two studs rather than bolts so it was easy to get anut on from below if I need to change the bag. I also cut holes in my rear wagon floor and put a big ribber plug in the hole directly above the top airbag Allen key bolts. That allows me to lift the carpet, pull the rubber plug, put in a long Allen key and take out the top bolts to drop the airbag out of the mounting in about ten minutes work rather than an hour crawling around under the chassis getting abent neck.

534255


534258
 

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Discussion Starter · #6 ·
Thanks goerdie4x4 that’s a lot of good information
I noticed a difference in the piston between the 5412 and 5429 bags.. would this different design make a big difference..?
I hade a quick look at my setup last night and noticed my rear spring seats line up fairly well with the tops but that might change once they get a bit closer together.. I currently have adjustable top arms and looking to put the weld on long arm bottom kit in at the same time I change over to bags..
 

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Thanks goerdie4x4 that’s a lot of good information
I noticed a difference in the piston between the 5412 and 5429 bags.. would this different design make a big difference..?
I hade a quick look at my setup last night and noticed my rear spring seats line up fairly well with the tops but that might change once they get a bit closer together.. I currently have adjustable top arms and looking to put the weld on long arm bottom kit in at the same time I change over to bags..
From talking to member Old Mav, he used the 5429 bags on his ute so see if you can find his build thread it's awesome suspension set up. He said it is much better ride and better suited to the weight of the Patrol than the more straight sided piston shape.

They each have different characteristics of how fast the piston travel causes air compression inside the bag and compared to the volume of the bag determines the relative change in spring rate during compression. They are so different from coil springs in some respects that it is hard to get the head around what actually makes the difference. Most conventional suspension shop guys just don't have a clue what is needed for airbags compared to coils. Shocks are quite difficult to get just right as their valving is all around the coil spring compression and rebound rates not airbags.
I have settled on fairly soft shock valving with the big Koni 90 the compression is quite soft anyway which gives me nice ride over corrugations. The rebound I have is probably a little bit too firm on the Koni set for coils which typically have a stronger rebound spring rate compared to the airbag. This is not bad on mine, but I do find it tends to make it squatt the rear end down over a series of big bumps or big corrugations, the strong rebound of the shock doesn't let the airbag spring rebound fast enough, so not enough time to lift the rear end back up before the next bump compresses it again, if you get what I mean. So driving into or out of a corrugated corner where the size of corrugations tend to get bigger, the rear end tends to sit it self down, then recovers again as I slow down or as I come out onto the straigt road with smaller corrugations. Doesn't present a problem just something to be aware of in the driving style to not let the bum end slide out.

Rear bump stops need to be looked at carefully. I was going to use 80 series bump stops at the rear chassis mount points, but they are bigger diameter base than the old Nissan bump stops are compared to width on the chassis mount they stick out further towards the side of the airbag and were going to rub on it. Most of the places that sell them make the bracket too far offset so the bump stop base clears the tyre, but that makes it closer to the spring. Coils are not as wide as the airbag so you have to be really careful with giving heaps of space and no sharp edges anywhere around the sides of the airbag all the way top to bottom. Coil tower brace brackets and even the bolts to the rear upper arms to diff bracket had to turn the bolts around so the point was away from the bag not towards it where it might just catch the edge of a thread and cut the bag.

You can see on my photo below, red arrow I have turned that bolt around so the point is out the other side.
Yellow arrow are the bolts on my Superior Engineering bolt in coil tower brace for the Wagon. I turned these bolts around too and eventually swapped them to round button head Allen key type with no sharp edges.
Green arrow there is a sharp square corner on each side of the factory chassis coil tower that sticks out too close to the bag, particularly when the bag comes up to full compression a lot of extra bag length gets folded over itself up close to the top.


534259


I have used pretty heavy rear Whiteline sway bar to control body roll with a rooftop camper on top it is a bit top heavy. Then with a firm but very flexible front superior engineering superflex sway bar, superflex hybrid front arms with the drop box type hybrid Toyota rubber bush chassis mount. The front allows a lot more flex and the slightly stiffer rear seems to make the front work better than it ever used to. Hence I have the same length bags and shocks front as well as rear, gives nice even travel on the rough stuff rather than lifting front wheels like it used to do.
 

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Discussion Starter · #8 ·
From talking to member Old Mav, he used the 5429 bags on his ute so see if you can find his build thread it's awesome suspension set up. He said it is much better ride and better suited to the weight of the Patrol than the more straight sided piston shape.

They each have different characteristics of how fast the piston travel causes air compression inside the bag and compared to the volume of the bag determines the relative change in spring rate during compression. They are so different from coil springs in some respects that it is hard to get the head around what actually makes the difference. Most conventional suspension shop guys just don't have a clue what is needed for airbags compared to coils. Shocks are quite difficult to get just right as their valving is all around the coil spring compression and rebound rates not airbags.
I have settled on fairly soft shock valving with the big Koni 90 the compression is quite soft anyway which gives me nice ride over corrugations. The rebound I have is probably a little bit too firm on the Koni set for coils which typically have a stronger rebound spring rate compared to the airbag. This is not bad on mine, but I do find it tends to make it squatt the rear end down over a series of big bumps or big corrugations, the strong rebound of the shock doesn't let the airbag spring rebound fast enough, so not enough time to lift the rear end back up before the next bump compresses it again, if you get what I mean. So driving into or out of a corrugated corner where the size of corrugations tend to get bigger, the rear end tends to sit it self down, then recovers again as I slow down or as I come out onto the straigt road with smaller corrugations. Doesn't present a problem just something to be aware of in the driving style to not let the bum end slide out.

Rear bump stops need to be looked at carefully. I was going to use 80 series bump stops at the rear chassis mount points, but they are bigger diameter base than the old Nissan bump stops are compared to width on the chassis mount they stick out further towards the side of the airbag and were going to rub on it. Most of the places that sell them make the bracket too far offset so the bump stop base clears the tyre, but that makes it closer to the spring. Coils are not as wide as the airbag so you have to be really careful with giving heaps of space and no sharp edges anywhere around the sides of the airbag all the way top to bottom. Coil tower brace brackets and even the bolts to the rear upper arms to diff bracket had to turn the bolts around so the point was away from the bag not towards it where it might just catch the edge of a thread and cut the bag.

You can see on my photo below, red arrow I have turned that bolt around so the point is out the other side.
Yellow arrow are the bolts on my Superior Engineering bolt in coil tower brace for the Wagon. I turned these bolts around too and eventually swapped them to round button head Allen key type with no sharp edges.
Green arrow there is a sharp square corner on each side of the factory chassis coil tower that sticks out too close to the bag, particularly when the bag comes up to full compression a lot of extra bag length gets folded over itself up close to the top.


View attachment 534259

I have used pretty heavy rear Whiteline sway bar to control body roll with a rooftop camper on top it is a bit top heavy. Then with a firm but very flexible front superior engineering superflex sway bar, superflex hybrid front arms with the drop box type hybrid Toyota rubber bush chassis mount. The front allows a lot more flex and the slightly stiffer rear seems to make the front work better than it ever used to. Hence I have the same length bags and shocks front as well as rear, gives nice even travel on the rough stuff rather than lifting front wheels like it used to do.
yeah nice work mate, looks like you have spent a lot of time and effort into this..
i am going to pray my shocks have enough adjustability to get what im after but i wont know until i try it..
your mounts you have had fabricated up look exactly what i plan to do with mine, was hoping to find someone around where i live that has a GU diff housing so i could get some CAD drawings made up to produce the mounts, as this time of year in Tassie i cant afford my ute being off the road to long as i use it to get wood..
i have the PSR coil mount bracing which links both the rear coil hats together so the bolts (yellow) shouldnt effect me..i have seen previously that i need to grind of the side of the coil housing(green arrow) and swap the direction of the bolts for the upper control arms..
Is the optimal ride height of the bags around half way between fully compressed and fully extended..?
i will have a look into Old Mav's setup to see what he has compared to yours.
 

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Yes the ute definitely has the advantage of more room above the coil towers to the tray for a nicer brace across the towers. That should save you a lot of drama compared to the wagon. Fitting those bolt in tower brace things nearly bloody killed me.

Definitely if you can get a spare diff housing to take your time with, then it makes things a lot easier. Mine was off the road for way too long but I also did a front diff laminated and braced and had the motor out for a rebuild so it all had to be done at once. Have a look at the other PSR diff brace brackets as well, might be worth strengthening the diff at the same time. Then checking it is still all straight after welding and painting it.

Regards ride height, yes somewhere around the middle range of the airbag length is the sweet spot for ride. If you look up your airbag number on TruckSprings USA, you can find a link to the pdf document from Firestone for the particular bag number. it has alot of technical data that OldMav might explain but got lost abit on me. But they do state optimum ride height. The longer bag generally has a longer range in the middle where it is good.

Below is a photo I think I pinched from @GQshayne of his 5422 and 5429 bags when he was changing over.
Photo is turned upside down to show the bag length difference and I was drawing on it to try and think how much extra bag fold over there would be top and bottom to make room for. They were going to be just a bit too long for my wagon, but would be perfect in a ute with more clearance all around.

I would really like to find a bag length somewhere between for mine. But my limitation is that I want to use the same front and rear plus carry spares for remote area, getting six new bags with todays US dollar prices and huge postage from the US is a bit out of the price range for me.

534262
 

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Discussion Starter · #10 ·
Yes the ute definitely has the advantage of more room above the coil towers to the tray for a nicer brace across the towers. That should save you a lot of drama compared to the wagon. Fitting those bolt in tower brace things nearly bloody killed me.

Definitely if you can get a spare diff housing to take your time with, then it makes things a lot easier. Mine was off the road for way too long but I also did a front diff laminated and braced and had the motor out for a rebuild so it all had to be done at once. Have a look at the other PSR diff brace brackets as well, might be worth strengthening the diff at the same time. Then checking it is still all straight after welding and painting it.

Regards ride height, yes somewhere around the middle range of the airbag length is the sweet spot for ride. If you look up your airbag number on TruckSprings USA, you can find a link to the pdf document from Firestone for the particular bag number. it has alot of technical data that OldMav might explain but got lost abit on me. But they do state optimum ride height. The longer bag generally has a longer range in the middle where it is good.

Below is a photo I think I pinched from @GQshayne of his 5422 and 5429 bags when he was changing over.
Photo is turned upside down to show the bag length difference and I was drawing on it to try and think how much extra bag fold over there would be top and bottom to make room for. They were going to be just a bit too long for my wagon, but would be perfect in a ute with more clearance all around.

I would really like to find a bag length somewhere between for mine. But my limitation is that I want to use the same front and rear plus carry spares for remote area, getting six new bags with todays US dollar prices and huge postage from the US is a bit out of the price range for me.

View attachment 534262
Yeah they seem a massive difference in height when side by side.. I’m considering measuring (between top and bottom plates) my height at the moment which is around 3” lift and full flex measurements sending them the measurements to the guys in the US to see what they think..I would assume the bags would all be around the same weight rating just the length and characteristic (piston) change
 

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I would assume the bags would all be around the same weight rating just the length and characteristic (piston) change
There are alot of different weight ranges for the bags. But theres only a limited range of bags that can physically fit where we need. There are separate code numbers on the actual bag to designate diameter and height etc.


Here is the link to the 5429 bag. The full part nunber is W01-358-5429. the bag only is 1T14C-8. I think the 1T14C designates the size diameter and type of rolling sleve bag or bellows, the -8 is the height or length range code. The cut away diagram is handy as it shows the top and bottom mounting bolts, the bump stop if it has one, the height range and piston shape. Sometimes there is the same bag number with several different options for top and bottom mounts for different vehicle fittment and hence different part numbers but same bag.


 

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Another supplier to check out too, SD Truck springs.

 

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Discussion Starter · #13 ·
Another supplier to check out too, SD Truck springs.

Thanks mate I’ll look into the 5429 bags this gives me a very good starting point all the info you have provided..
 

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Firestone recommend the 5429 for our vehicle. Oldmav corresponded with them some time ago.

Here are some specs for the 5429. These are very hard to find on the internet now. Of particular interest to you will be the design height. This is your ride height distance you will need, between top and bottom mounts. Second graph shops load capacity at various pressures.

534264


534265


As for suspension, my experience is that a damper valved for a coil spring will be very harsh in its action when matched to an airbag. Much has been written about this already so I won't repeat it all here. The basics of it are that an airbag has a lot less need for damping compared to a coil. Especially when it comes to rebound, you will have quite limited action/travel of the bag as the damper prevents it form moving as it needs to.
 

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Discussion Starter · #15 ·
Firestone recommend the 5429 for our vehicle. Oldmav corresponded with them some time ago.

Here are some specs for the 5429. These are very hard to find on the internet now. Of particular interest to you will be the design height. This is your ride height distance you will need, between top and bottom mounts. Second graph shops load capacity at various pressures.

View attachment 534264

View attachment 534265

As for suspension, my experience is that a damper valved for a coil spring will be very harsh in its action when matched to an airbag. Much has been written about this already so I won't repeat it all here. The basics of it are that an airbag has a lot less need for damping compared to a coil. Especially when it comes to rebound, you will have quite limited action/travel of the bag as the damper prevents it form moving as it needs to.
Thanks mate, yes I think I understand the rebound for the shocks.. I know my shocks won’t be the best setup for the airbags but hopefully not to bad.. my shocks are rebuildable so when they **** themselves hopefully I can get them re valved more to suite..
 

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My experience is you will need a bit less compression across the stack. Rebound is different though. Go too light at the top of the stack near the piston and you will lose control and be nasty. So you need to keep some valving in the free bleed, and then moderate control near the piston, then it gets lighter in the mid and high speed section of the stack. It is a lot less progressive compared to a coil stack.
 

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Discussion Starter · #17 ·
My experience is you will need a bit less compression across the stack. Rebound is different though. Go too light at the top of the stack near the piston and you will lose control and be nasty. So you need to keep some valving in the free bleed, and then moderate control near the piston, then it gets lighter in the mid and high speed section of the stack. It is a lot less progressive compared to a coil stack.
Thanks mate, I’ll keep these as notes for when they give out and get them rebuilt to hopefully something like your describing
 

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The catch will be what the basic design of the shock is. I have Radflo now and capacity to flow oil is much greater than the previous first generation Superior shocks I had. They changed the design to allow more bleed on the second design, so I cannot comment on them.

The issue I had was that I was going lighter in the valving without result. I could not get the suspension to work, it had very limited travel at even moderate shock speeds. Some dodgy experimenting showed that this could be fixed with lighter valving, but the shocks would not allow me to do it using the standard design. I needed more oil flow, and could not get it with those pistons. Once I switched to Radflo, it was a different scenario immediately. The basic design allows for enough flow through the pistons which then you can tune via the shim stack - as it should be.
 
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