Are Air bags worth it?

Submitted: Friday, Nov 10, 2017 at 14:04
ThreadID: 135853 Views:4033 Replies:15 FollowUps:3
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Hi all, my son is contemplating putting air bags in the rear of his 76 cruiser. I've never really heard good things about them, always leaking, getting punctured, air lines being ripped off.. just like to hear some experienced thoughts from those that have had/used them, both good and bad... thanks all.. Odog
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Reply By: DesF - Friday, Nov 10, 2017 at 14:28

Friday, Nov 10, 2017 at 14:28
Hi , I have had PolyAirs in the rear of my NF Pajero for 15years , and have just replaced them this year as they finally perished in the lumps between the coils,

They are great, I just run 5/6 lbs empty and when we go north camping etc I use about 15lb ( just bring it back up to empty height ) and use 18lb with the Jayco on the back and Engel etc on board.
Never had a hose problem in fact I used the old hoses and valves with the new bags. Have done heaps of Outback travelling . Finke , Birdsville , Innaminka etc,
and no problems ,
Just remember to blow them up before you load up, as they are not meant to lift a loaded 4x4,
Cheers Des.
AnswerID: 614888

Reply By: baznpud - Friday, Nov 10, 2017 at 15:21

Friday, Nov 10, 2017 at 15:21
We have a 100 series cruiser (2002 V8) had bags in it since new, done nearly 300 thousand ks with them and not one problem.
Go caravaning, life is so much shorter than death.

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AnswerID: 614891

Reply By: Notso - Friday, Nov 10, 2017 at 15:55

Friday, Nov 10, 2017 at 15:55
A friend put Firestone Airbags on his ute after the leaf springs sagged. He reckons they're good.
AnswerID: 614894

Reply By: RMD - Friday, Nov 10, 2017 at 16:43

Friday, Nov 10, 2017 at 16:43
On a previous vehicle, HJ61 cruiser, I used Firestone rubber bellows bags for 15 years, on the rear to assist with carrying load and to provide a distance of compression of the suspension so bottoming was not happening, ie, good travel upward. Worked well with heavy internal load and towing a T van in some rough areas. No bottoming = no sudden stress on chassis and components.

Apart from an intial leak of air from the crappy sealant already on the fittings which was rectified with some Loctite plastic sealant, I had no trouble and still have them to use on another vehicle.
AnswerID: 614895

Reply By: Member - Mark (Tamworth NSW) - Friday, Nov 10, 2017 at 18:11

Friday, Nov 10, 2017 at 18:11
As someone who needs stronger rear suspension for just 2-3 weeks per year, they are a great solution.
Probably done 200000km in them over the past 5 years, probably 30 000km of that gravel/dirt
Yep had one leak, but if buying another vehicle tomorrow I would fit them
At the same time I upgraded the rear dampeners in my Pajero

I'm told they are disastrous for leaf suspension, ultimately frame will crack
AnswerID: 614897

Reply By: Batt's - Friday, Nov 10, 2017 at 18:27

Friday, Nov 10, 2017 at 18:27
I had lots of trouble with Airbag man's blue bags splitting and leaking at the base of the valve on a Disco
Never had any problems with Polyair bags they were great lasted 9yrs inside the rear coils on a GQ.

I currently run Boss air bellows on the rear of a GQ which have replaced the coils they work well also my neighbour has Boss load assist air bellows we fitted to his leaf sprung 2007 BT50 to support his canopy they work very well and are constructed of heavy duty material like mine so they can take a battering. Never had an air line ripped off you have to look at where the hoses run and where the inlet valves are placed keep them out of harms way will help a lot.

Before he gets anything he has to look at what he needs them for because a spring up grade may be all he needs coupled with a quality shock to control the extra jarring the heavy springs may create so you still get a good ride. Air assist bags are only really designed to do that assist when carrying temporary heavy loads or towing trailers or vans to level the ride back up. One of the main problems people have trouble with is they now believe they can carry more weight which can have expensive complications so when used correctly they are great if not they may bite you in the arse as many people have found out.
AnswerID: 614899

Reply By: Member - Ross N (NSW) - Saturday, Nov 11, 2017 at 17:38

Saturday, Nov 11, 2017 at 17:38
Am I right in thinking that rear airbags on a leaf sprung vehicle puts most stress on one point , the airbag, as against the otherwise two points of the leaf spring?
Perhaps some of the engineering types on the forum can enlighten me.
AnswerID: 614912

Reply By: Member - Scott & Sally - Saturday, Nov 11, 2017 at 19:45

Saturday, Nov 11, 2017 at 19:45
G'day Odog,

I've had air bags on the rear of my 76 and have never had a problem.
I tow an off road camper with a tow ball weight of around 180 kg. When just doing my day to day I've got 5 to 10 psi in them and when towing I never go above 35 psi. Air bag assist is just what it says it's to assist the springs not take over from them.
If by some chance the rear end was still sagging I would definitely look at a more robust spring package before using the air bags to take up the the sag.
Don't forget that the top mount of the air bag is mounted where the rubber stopper is remover from and is not a reinforced part of the chassis.
This is were everyone who has bent a chassis has come unstuck (mainly through over inflating them) just because they're rated for say 200 psi never run that pressure in them.

Cheers Scott
AnswerID: 614915

Follow Up By: Batt's - Tuesday, Nov 28, 2017 at 13:24

Tuesday, Nov 28, 2017 at 13:24
180kg is a lot of ball weight for a camper trailer to have I would question how the weight is balanced because the camper or whatever item in tow should support most of it's own weight. When set up correctly the van etc will ride better because it's suspension is working correctly and not placing unnecessary weight forward onto the tow vehicle which puts more strain on it's suspension causing it's bum to drag around. Then to compensate for that in some cases extra heavy duty suspension in required to support the additional weight because the rear of the vehicle itself will be loaded as well. Adding a heavier rated spring is fine but some people tend to go overboard with this, go to heavy which gives them a terrible ride when empty.

I had a van yrs ago and when loaded at 1,400kg it had a tow ball weight of just 80kg. I didn't need to upgrade the springs rating I did fit air bags though because the rear of the vehicle was packed as well. But on our journey from Perth to Mackay the air bags where useless as they kept blowing so 90% or more or the trip was done without them and the vehicle still sat level because I made sure I set it up correctly in the first place so I didn't have to rely on the air bags. They were there just to assist and help preserve the coil springs for the long term.
FollowupID: 886135

Reply By: Member - J&A&KK - Sunday, Nov 12, 2017 at 01:17

Sunday, Nov 12, 2017 at 01:17

We ran Firestone airbags on many survey vehicles. In general the vehicles were replaced every 6 years and had done about 300- 400,000km. So I cannot really comment on longevity greater than this.

Leaks - none that I know of
Punctures - none that I know of
Lines ripped off - none. However judicious routing of the air lines is required.

You can assume from this that reliability was very good.

With coil springs we lately used the high pressure unit. The air bag was mounted inside a Kevlar ( or similar) cylinder that sat inside the coil springs. This ensured the airbag was not in contact with the spring itself.

The question of using airbags or a suspension upgrade is always worthwhile asking. But beyond my knowledge to answer.

Cheers John

AnswerID: 614917

Reply By: Member - Odog - Sunday, Nov 12, 2017 at 10:28

Sunday, Nov 12, 2017 at 10:28
Thank you to all, for the information. I know that all this has been a big help, I'm sure after reading this, the lad will sort out a set to suit his needs.. from what I've read, they do sound very handy, when used correctly... thanks again for your help.. cheers Odog
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AnswerID: 614922

Reply By: splits - Sunday, Nov 12, 2017 at 15:51

Sunday, Nov 12, 2017 at 15:51
Many people have used them for years and never had a problem while there is no shortage of owners who can not say the same thing. A lot depends depends on what he intends doing with them.

They are exponential springs. i.e. the more you compress them the more they resist further compression. Leaf or coil springs compress in proportion to the load. They will keep compressing until the chassis reaches the bump rubbers. Bump rubbers are also exponential and will bring the chassis to a sudden but slightly cushioned stop. An air bag can become like a rock by the time it is about three quarters compressed. That has caused serious damage to many cars but once again it depends on how they are being used.

Any stiffening of the rear suspension will transfer more weight to the outside rear wheels in corners or sudden swerves. That can result in the car oversteering. Just about every manufacture designs their cars to understeer because the average driver usually has a lot of trouble trying to control oversteer. The charts mixed in with these photos will give you a good idea what suspension alterations will do to a car.Under/Oversteer This could become a problem for your son in some driving situations, particularly if he is towing something long, high and heavy like a large caravan.

Tell your son to ring this company and discuss it with them. They have been in business since the 1950s and started Polyair. They can sort out everything from his Cruiser to his Ferrari if he happens to have one.Heasmans
AnswerID: 614926

Reply By: Member - Phil G (SA) - Sunday, Nov 12, 2017 at 20:04

Sunday, Nov 12, 2017 at 20:04
76 series has rear leaf springs. Airbags will reduce articulation significantly so it will lift wheels easily when 4wding. Not a good idea - I had them on a 79series but would not go that way again.
Coil rear end vehicles are OK.
AnswerID: 614933

Follow Up By: Batt's - Sunday, Nov 12, 2017 at 21:57

Sunday, Nov 12, 2017 at 21:57
That where choosing the correct leaf springs would probably be the better option. I personally wouldn't be doing harder off road tracks including sand or desert with pumped up air bags on a leaf sprung vehicle you would be increasing the risk of damaging the chassis it might be ok for lighter loads but not heavy.
FollowupID: 885651

Reply By: David W85 - Sunday, Nov 12, 2017 at 21:53

Sunday, Nov 12, 2017 at 21:53
Have polyair dominator bags with the dislocation cradles fitted to the rear of my 76 so far so good.
AnswerID: 614936

Follow Up By: Member - Odog - Monday, Nov 13, 2017 at 19:13

Monday, Nov 13, 2017 at 19:13
Hi David, how does it handle off road, notice a difference?
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Reply By: Trawe - Wednesday, Nov 15, 2017 at 15:57

Wednesday, Nov 15, 2017 at 15:57
Hello Odog
Have Airbag man on my 79 series. Yes I have a leak in one airline but up until this happened they are worth the money.
AnswerID: 614975

Reply By: mynance - Sunday, Nov 19, 2017 at 12:24

Sunday, Nov 19, 2017 at 12:24
I have found airbags to be excellent on a monocoque chassis but ladder framed chassis may bend.

AnswerID: 615081

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