Polly Bag Suspension

[rochjas]

Guys,

Just starting to look around my new purchase - 2005 GU IV Patrol 3.0TD Auto. Noticed that its got Polly bags in the rear. When not in use what should these be at (air wise). Any help would be great.

Thanks


Jason

[Bigrig]

Just plain empty mate - let the air release from the valve till they stop and that's it. Many keep air in them, but I found when I got my truck which had poly bags originally (ripped them out) that it a bit too rigid driving around town with them aired up - saves the springs no doubt, but made for an uncomfortable ride. Use them for load carrying only to assist the springs and bobs your uncle.

[rochjas]

Just plain empty mate - let the air release from the valve till they stop and that's it. Many keep air in them, but I found when I got my truck which had poly bags originally (ripped them out) that it a bit too rigid driving around town with them aired up - saves the springs no doubt, but made for an uncomfortable ride. Use them for load carrying only to assist the springs and bobs your uncle.

Thanks Bigrig

Going to keep them in the GU as I am collecting my new Camper Trailer in just over a week.... But will let the air out of em tonight. When filling them what PSI do I place in them...Thanks again

[MudRunnerTD]

Sorry Scottie not quite right.

The Poly bags need to have at least 5psi in them constantly or you will wreck them driving day to day. Your springs will move around enough to tear and pinch them.

When pumping them up i would generally go to your tyre pressure or less. I have run mine at anywhere from 18psi to 35psi depending on your load.

To be honest though the Polyairs are not as good as a correct rated spring and if you are going to do a 2inch lift or something then consider your usage and buy the appropriate spring and pull them out.

Have fun

[Bigrig]

Sorry Scottie not quite right.

The Poly bags need to have at least 5psi in them constantly or you will wreck them driving day to day. Your springs will move around enough to tear and pinch them.

When pumping them up i would generally go to your tyre pressure or less. I have run mine at anywhere from 18psi to 35psi depending on your load.

To be honest though the Polyairs are not as good as a correct rated spring and if you are going to do a 2inch lift or something then consider your usage and buy the appropriate spring and pull them out.

Have fun

Yes, true glass slipper (grasshopper!! lol) but I was told if released from the valve, they only drop to the bag pressure which is around 4-5psi due to the 'firmness' of the poly itself ... happy for this to be wrong, but that was from the horses mouth who installed them ... and when I emptied mine (whilst on flat ground) they stopped running air out the valve and held about 4-5psi as said ... was I just lucky?? Be a first!!!! lol

[daggy]

x 2 on 4-5 psi otherwise they can get piched by the spring. I have airbags with a 2" lift, they are great for the odd times that I load up the truck or tow the trailer, otherwise i have relatively light spring for the comfort.

[Silver]

Looking at advice on running them empty - looks like it has worked this far for Bigrig! Instructions only take one so far :-)

I have the blue firestone ones, not the red polyairs. The recommendation on the paperwork is 5 psi min, 35 max - but t here are some more detailed instructions about getting under with a straight edge, and checking how far the bag protrudes into the coils.

Let me know what colour yours are, if blue, I'll dig out the instructions and reproduce here. Airbagman might have the info on their own site?

The red ones are supposed to be pumped up to pressure, then loaded up. That is the reason I went for the blue ones, they expressly say you can load up, then pump up back to level.

Lifts - to run the blue ones with a 2" lift, a hard plastic cup is supplied. Goes at the bottom of the coil, then bag sits on top. Would have to get under and have a look to see if it interferes with up travel. The airbag takes articulation away to some degree I think.

Just recently some posted on another thread here, that an airbag loads up the spring mount and can cause cracks. The impression I came away with was that the airbag at higher pressure has little give, which translates into higher shock loads on the mounts. There are braces available to help with this - if carried to the next step, I guess the chassis might be next in the firing line. Best solution is to leave some of the weight at home?

[nissannewby]

I would also be doing a thorough inspection on your rear coil towers. These are known to tear away from the chassis with large loads on them consistantly and being that it has air bags I would be having a good look. The last thing you want is for these to come away from the chassis. Superior do brace kits for the towers and are well worth the money if you are going to be doing a fair bit of touring loaded up and towing a camper.

[patch697]

Yes, true glass slipper (grasshopper!! lol) but I was told if released from the valve, they only drop to the bag pressure which is around 4-5psi due to the 'firmness' of the poly itself ... happy for this to be wrong, but that was from the horses mouth who installed them ... and when I emptied mine (whilst on flat ground) they stopped running air out the valve and held about 4-5psi as said ... was I just lucky?? Be a first!!!! lol

You must have been bloody close to being on the money Bigus cos Tony sent your old airbags down to me well over a year ago & they're been in my Rig working perfectly ever since.

I run a constant 10 psi in them as the Mav is a toolbox on wheels & rides very well, Its when I emptying the back of the Mav to go out wheeling they really come into there own cos I do exactly what you did when you had them & yes, that drops them to between 4&5 psi (yes I do check them) which I find is just perfect to go out wheeling all day & them come home load the Mav back up & run them right back up to 10psi......

I know there not everyone's cup of tea but for me they offer the best of both worlds.

[Morton]

ditto to Nissannewby & Silver, the upper rear spring hangers have a tendency to fail under heavy loads with airbags, people tend to over-inflat them when heavily loaded, this is mostly from rough corrugated dirt roads etc, basically a constant pounding, it is fine on the blacktop as it doesnt pound the hanger much, generally on rough corrugated roads you should lower the pressure in them & the ride will be superb, up it a bit when back on the blacktop, there are aftermarket hangers for them as stated earlier that are much stronger, it is a less commonly known failure of the mighty Nissan, you should check it periodically & look forsigns of the upper hanger tearing away

[rochjas]

Looking at advice on running them empty - looks like it has worked this far for Bigrig! Instructions only take one so far :-)

I have the blue firestone ones, not the red polyairs. The recommendation on the paperwork is 5 psi min, 35 max - but t here are some more detailed instructions about getting under with a straight edge, and checking how far the bag protrudes into the coils.

Let me know what colour yours are, if blue, I'll dig out the instructions and reproduce here. Airbagman might have the info on their own site?

The red ones are supposed to be pumped up to pressure, then loaded up. That is the reason I went for the blue ones, they expressly say you can load up, then pump up back to level.

Lifts - to run the blue ones with a 2" lift, a hard plastic cup is supplied. Goes at the bottom of the coil, then bag sits on top. Would have to get under and have a look to see if it interferes with up travel. The airbag takes articulation away to some degree I think.

Just recently some posted on another thread here, that an airbag loads up the spring mount and can cause cracks. The impression I came away with was that the airbag at higher pressure has little give, which translates into higher shock loads on the mounts. There are braces available to help with this - if carried to the next step, I guess the chassis might be next in the firing line. Best solution is to leave some of the weight at home?

All, I have the red ones. Had a look at the hangers and all appears ok. Looking at the coils they look newish too.... Yellow in colour.

[Silver]

Red ones are poly-airs - It could be that there is another brand that is red, but I don't know of it. They seem a popular choice too. Maybe if you find their max and min pressures and any other way of measuring same you could share it here?

Per the instruction sheet, for the GQ, airbagman recommended 5 - 35 for the firestones, that said, I have never had mine above 15 psi.

The instruction sheet for my AirbagMan Coil Rite blue firestones includes:

NEVER EXCEED THE MANUFACTURERS WEIGHT RATINGS FOR THE CHASSIS.

Air pressure information.
Only inflate air bellows to level vehicle.
Maximum air pressure - air bellows must not extend more than half waythrough the coil springs at maximum inflation pressure.
the maximum inflation pressure must be set when the vehicle is in the fully loaded condition
If bellows extends more than this it is likely to burst.

In the interests of completeness I went looking for mrairbagman on line, they stock the firestones/blue ones. I found a site which is in the process of being updated apparently http://www.airbagman.com.au/ Torq 4x4 who are fairly active on here stock the firestones - the blue ones, - since that post my search flushed out things may have changed so anyone interested in either brand perhaps give them a call? there are a few sites that compare the various options.

Like many things, airbag helpers are perhaps a compromise. If you were looking for max articulation, you would avoid them. If you were looking to exceed the original max load rating, there are better solutions. But they work ok for me in that space in the middle - levelling up the rig when it has a fair old load aboard, but not a massive one!! In saying that, it doesn't take long to use up the rated load capacity of a wagon by the time a few accessories go on, rack, drawers, extra wheels, carriers for same, bar work, winch, roof rack load, sliders, bigger fuel tank, dual fuel, passengers etc etc. Maybe one day I'll go and look it up :-)

[happygu]

I would pull them out and sell them if you are planning any serious outback trips.

If just tootling around town, then they will probably be ok.

Best of both worlds would be to add the rear spring tower strengthening kit, and then you can leave them as they are. It normally costs me around $300 for strengthening gussets to be welded in, but would cost a little more for the bolt on kits that are out there.

Mic

[my third 256]

I would pull them out and sell them if you are planning any serious outback trips.

If just tootling around town, then they will probably be ok.

Best of both worlds would be to add the rear spring tower strengthening kit, and then you can leave them as they are. It normally costs me around $300 for strengthening gussets to be welded in, but would cost a little more for the bolt on kits that are out there.

Mic
here is a link to a mob in melbourne that do the strencthoning kits $300 to buy and $300 to install its the 3rd to last item
http://atocauto.com.au/

[happygu]

My Third - Cheap Insurance I think

Much cheaper than a roadside repair.....

Mic

[Silver]

If you look under heavy vehicles you will see a lot that are sitting on airbags and nothing else. Used the right way in the right application airbags are the right suspension solution. These are stand alone airbags, not constrained by coils, but there must be something that controls their diameter.

I am not an engineer, a suspension expert, or anything like that, just an interested Patrol driver. Silver is not set up for touring, but has just gone from ARB/OME 'comfort' rated suspension to TJM with heavy duty rears.

What is the max load? Page 84 of my Maverick's owners manual says:

.............................Pick up........Chassis Cab.............Wagon Std..........Hardtop XL
Payload (KG)..........1185...........1345................. .......815.................... 855

'Payload' is not defined, but my guess it includes everything, including passengers, but not full standard fuel tanks etc. If anyone knows, please share :-)

Perhaps the blue oval takes away a few KG from the total compared with a genuine Nissan. Perhaps GUs being inherently superior can just add a few 00s :-)

In any event, GQ wagon owners, esp those set up for touring would have little trouble hitting the limit stated by Nissan. Us too, just going on holidays, I reckon. Bullbar, tow bar, roof rack, 2 adults, 1 kid.............

I wonder whether suspension manufacturers have a higher figure they use as a standard when they design their packages? Again, if anyone knows... please share?

Manufacturers of coil helper bags, the ones that go inside the coils, like we are discussing here say they do not increase the designed maximum load. (I'm going to be la2y and just call them airbags.) The airbag manufacturers warn against exceeding the max load.

I'm curious whether airbags are any more destructive than heavier rated coils.

I'm curious about the load at which something else fails, eg chassis, if the coil mounting hardware is reinforced. I appreciate this is affected by a lot of variables.

I reckon Silver has taken a hit on articulation due to airbags, even if at min pressure of 5 psi, and also because of the move from comfort rating to extra heavy duty. I have no evidence for this, didn't measure before and after.

There is no evidence in Silver of cracking etc - but we are not working the system hard. It is nice to be able to load up, pump up, have the lights on the road and out of the trees, and not be flashed by oncoming traffic.

[happygu]

Silver,

Ever since moving from the MQ to the GQ's and then later on the GU's, I have heard all the stories about weak rear spring towers on the patrol. I had my GQ for over 12 years, lived in Alice Springs for quite a while, and travelled regularly on all the 'bad' roads which were supposed to be the ones that the Patrol's rear spring towers couldn't handle, and have never had any issues - the only thing I ever had was a crack in the rear diff housing which I had welded up in Alice and never had any issues after that.

The only caveat to that is that I travel fairly light, and although i have heaps of stuff in my car ( and sometimes amaze people with what is in there, as I can normally still see out of the back windows on a trip ), I have seen so many other travellers which I can only describe as overweight and overloaded, as the amount of stuff they carry would cetainly put their vehicle over the maximum payload. :icon_bonk:

I used to just run normal 2" lifts on my Patrols, so with minimal weight and softer springs I didn't see that the rear spring towers were ever a problem, and I certainly have never had any problems at all.

Now I run a slightly higher Lift with heavier rate springs, and after seeing quite a few others with problems with their rear spring towers over the years, My thought process says that if I am going to be travelling on heavily corrigated roads, that it is good insurance to have the rear spring towers strengthened and gussetted before anything may happen. I have had the last two vehicles done by the same 'reputable supplier', but I have noticed that they have been both done differently to each other. Did my supplier do it the right way the first time, and not the second, or did they find the first method didn't work as intended? - Don't know. Is this any guarantee against failure? - I would like to think so, but I guess anything can still happen.

There are plenty of stories of people paying $5K and up to have chassis repairs done after the rear spring towers have ripped off, and the common themes always are load and usually helper airbags. I have never used the helper airbags, so I am not trying to condemn their use as after all, as I can clearly see benefits with their use, but the internet is the internet....... we can't see what other people are doing, others definition of overloaded could be different to mine, and the stories are starting to add up ( Bit like the 3Litre Patrol engines..... ). There was a thread just days ago from a traveller stuck in Broome with the rear spring tower issue. They have airbags, but we can't see what they are carrying, we don't know how fast they travel, how they approach washaways, we don't know what they have done in their vehicle....... all we can do is to take note of what has happened.

I have chosen to get mine strengthened beforehand, small dollar outlay on a $50K plus vehicle, and thesedays, there are kits available off the shelf which may be even better than what I have had done.

All you can do is bring it to people's attention if they ask, as the traveller's stuck in Broome at the moment sure didn't know about any issues with heavy loads and airbags, and they might have found it handy to know before they left for their trip.

NOTE : There are probably heaps of vehicles out there with airbags and no issues, just like 3Litre Patrols.......:tongue:

Mic

[Silver]

Thanks for all the info above. Mic, really appreciate your post above.

If we ever plan to hit the dirt in serious quantities esp corrugations, reinforcing will go in, without question. All too true that it is better and cheaper to prevent the failure than fix it, and then put the protection in.

Knowing the weight aboard is key - might burn a tip voucher and do a lap of the tip weighbridge :-) Or open up the yellow pages for public weigh bridges.

Last time we went to Weipa and a touch North, towing a 4.5 m tinny on a reasonable trailer, it was ama2ing what rattled off or became loose, both on my mate's rig, and others stopped along the way. The road surface generally was pretty good, apparently it gets better each year.