In the distant past I've had 2 sets of plastic bags fitted to an old Range Rover inside the rear coils. I was most happy with the first set and they lasted for a few years of hard work before one failed at the air inlet point. I had a coil snap at one time and it rode along on the collapsed spring and the airbag without puncturing it and with just a slight rub mark. I'd guess that this had happened about a few hundred K's before hand but there was no indication of any problem. Only noticed it in a car park that there was a slight lean to one side. Due to not needing to carry any large loads for a few years I didn't bother replacing them after the stem failure after about 3 years.
It's the experience with the 2nd set though that has me refusing to ever use that type again and I wouldn't recommend them to anyone, but that's my personal opinion.
Due to having had them before and knowing that they must be kept with about 10 PSI in them at all times and a maximum of about 30 PSI plus using them frequently I did know how to treat them. Despite this they only lasted just over a year until neither one would hold any pressure at all. It didn't take much of an inspection to find out why. The synthetic material had gone brittle for quite a proportion of each bag.
I contacted the maker/supplier about the issue and to seek a replacement set but was refused as they were out of warranty, but not by much. I was told that I had not maintained them correctly. End of discussion apparently. End of my support as well.
Now I've seen this type of failure in a synthetic material before and it was in soles of footwear. Both in safety boots at work and with some pairs of kids shoes this was apparently due to a couple of reasons. One reason given was lack of use with no flexing of the material but the other reason was just aging of the material. In some kids shoes we bought one time and were stored until he had out grown the old pair but the first time he used them and with walking across the floor the sole was sticky and left material at every step. When severely flexed by hand the soles split in multiple places. A complaint to the maker and after giving them one to test they found that the shoes were very old stock and had apparently been sitting on a store shelf for a year or so. They apologised and sent us a replacement pair. The ultimate I saw for myself was in clearing out a locker at work and finding a pair of safety boots that belonged to a staff member that had long since left the Company. When I picked up the boots there were no soles on them at all. On the bottom of the locker was a heap of granulated material about the size of instant coffee.
My opinion of the failure of my set of air bags is that they might have been old stock that had been on a shelf for quite some time and perished like the shoes/boots I mentioned. If the manufacturer wasn't prepared to support their product, then neither will I.
My choice these days is to upgrade the springs as a first choice for heavily loading a vehicle. For rear coils it isn't particularly difficult to do them yourself and can be done quite quickly. Fitting a better set just for trips is quite possible, plus you can then carry the old ones if you want spares.
have had no probs.
