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