Air bag suspension as helper springs

Submitted: Saturday, Dec 14, 2013 at 09:55
ThreadID: 105484 Views:12528 Replies:14 FollowUps:6
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Hi I own a GU tray top with a slip on alloy canopy. We did a trip down the CSR in July and absolutely loved it. Great vegetation after a couple of good years. If you are thinking of going, do it in 2014 but use your UHF on channel 40 and call every couple of hills please?

Back to springs. My GU has 50mm lift using EFS shocks and springs. Did not experience any problems with them on the CSR. I also had the poly type bags in the coils, but on rough terrain you have to take most of the air out to get full suspension movement in the rough stuff. So I had rear end sag given the load needed on the CSR. When I did pump them up after the Canning It was still difficult to get the ride height up to level. Maybe I needed more spacers under the bags?

I am thinking of fitting the rubber type air bags as helpers to give me the rear end lift I need occasionally. My question is do they give enough suspension travel given the 50mm extra travel I have now?
Has anyone done this and was it a good experience?
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Reply By: Mick O - Saturday, Dec 14, 2013 at 10:25

Saturday, Dec 14, 2013 at 10:25
Paul,

The airbags will be of great assistance to you but I think that you would probably be better off reviewing your suspension set-up and adding the airbags as a part of a suite of options.

On these trips you are obviously heavily loaded and if you have rear end sag, you may be better off having EFS upgrade the spring pack to cater for the load. This may make it a little rougher when unloaded but I presume the travel rig is not the everyday town car when not travelling. The airbags should only be used to supplement existing suspension rather than act as a replacement which is what you sound like you will be using it for. You shouldn't have to use the bags to lift the rear of the vehicle several inches to get it back level, rather your fitted suspension should be at, or only a little under your preferred ride height when fully loaded. The airbags are then used to assist the load remain at this height rather than trying to lift it back up.

One of the key dangers in using the bags to lift a heavy rear-end is damage to the diff and axle housings or the chassis itself. They can fracture where the mounts sit because of the stresses applied when the bag becomes the principle method of support.

I've had EFS customise my spring pack to cater for exactly the issue you outline. I'm using a single piece bag that caters for a 4" lift. There are a variety of bag sizes in the bellows type airbags that should cater for your 50 mm lift. You should have your full range of movement provided you didn't use the bags to jack the vehicle up several inches in height. This implies that you will be using high pressure in the bags and as a result, you will lose compression ability

As an aside, next time you are fully loaded, drop those two wheels off the rear and see what sort of difference that makes to the ride height. Like you I have over 100kgs of tyre sitting right at the rear of the vehicle well past the rear axle. It makes a huge difference to the suspension if they could be bought forward. I'll be taking care of that little project in the next set of camper mods.

Cheers Mick
''We knew from the experience of well-known travelers that the
trip would doubtless be attended with much hardship.''
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AnswerID: 523050

Reply By: splits - Saturday, Dec 14, 2013 at 11:37

Saturday, Dec 14, 2013 at 11:37
"but on rough terrain you have to take most of the air out to get full suspension movement in the rough stuff. "

A feature of air bags that is not generally understood is they are exponential springs while a coil is linear. A coil is rated by the amount of weight that will compress it 1 inch. A 200 kg coil for example will compress 1 inch when 200 kgs is placed on it. 400 kgs will take it down 2 inches. 600 kg will compress it 3 inches and so on. An air bag just gets progressively harder the more you try and compress it. This is why you had to let air out of yours in order to get a bit of suspension travel. Your fully inflated air bags were just acting like oversize bump rubbers which are also exponential springs.

This is why so many utes with air bags, and far too much weight on the back, bend their chassis. The section of chassis behind the bags is like a long lever. As the chassis falls when the wheels drop into a depression in the road, the load out the back falls generating forces far in excess of the static weight' It then wants to keep going down but the rapidly hardening air bags bring it to a sudden stop. The end of the chassis, or lever as it has become, is given a hell of a whack down placing tremendous stress into the chassis in the area around the top of the bags. This is where the damage will eventually occur.

Former GM engineer and electronics genius Collyn Rivers, writing in answer to an air bag question on the Caravaners Forum a couple of years ago, said they are useful, with a little bit of air in them. for softening the ride of a harsh riding unloaded ute but they are not intended to fix sagging suspensions or for carrying extra weight.

Some people may disagree and point out that there are air bag suspended cars and trucks that have come from the factory that way. That is true but if you cast you mind back to the rubber cone suspended Mini in the 1960s, you will see that it used tapered rubber blocks as springs and tapered rubber blocks are still used to this day as bump rubbers. The tapered cones in the Minis were positioned front and rear so maximum movement up and down of the wheels resulted in considerably less compression of the rubber. They went from being the spring for a certain distance then became the bump rubbers.

What the factory engineers do with rubber blocks and air bags can be vastly different from what adding similar aftermarket parts can do to a car not originally designed for them.
AnswerID: 523054

Follow Up By: Nomadic Navara - Sunday, Dec 15, 2013 at 21:13

Sunday, Dec 15, 2013 at 21:13
He posted more today - link

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Reply By: olcoolone - Saturday, Dec 14, 2013 at 11:39

Saturday, Dec 14, 2013 at 11:39
I would try and stay away from airbags, airbags are a cheap option that is no match for a properly designed suspension system, most choose airbags as they know no difference, like to follow the trend, don't understand suspension, don't want to spend the coin or think heavy springs will make it ride harsh.... all misconceptions.

A properly designed suspension system using springs and dampers will out perform a poorly designed airbag set up hands down, the other thing to consider is if a bag or airline failed.

Spend the money and get someone who knows suspension inside out to set up you vehicle and you will not look back.

We have had three different suspension setups in our 200 series to get it to what we want and make it work, sure it takes time and money but the benefits are worth it.

Remember aftermarket off the shelf suspension is designed for the masses, there are other options available.


AnswerID: 523055

Reply By: exmouth1 - Saturday, Dec 14, 2013 at 15:44

Saturday, Dec 14, 2013 at 15:44
G, day powernut,
I can only agree with the replies the others have posted, I have 08 troopy that weighs somewhere near 3300 kgs, I got arb to upgrade the springs and install a 50mm lift. The 1st set of rear springs were 600kg rated and after 1 trip it was starting to sag a bit, I got them to install 800kg rated rear springs and that has fixed the problem, it also rides very well, not harsh at all. I looked into airbags but was advised against them as they put too much pressure on the chassis causing it to crack or bend.
Get your suspension upgraded.
Cheers
John
AnswerID: 523064

Reply By: troopy 47 - Sunday, Dec 15, 2013 at 06:45

Sunday, Dec 15, 2013 at 06:45
Going trough that now with dual cab landcruiser have heavier springs with caravan on it drops around 45mm not sure if airbag helpers with all that overhang is a good idea. Not sure if i want heavier springs because of firmer ride when unloaded which is a lot of the time.
AnswerID: 523075

Follow Up By: Member - Ross G5 - Sunday, Dec 15, 2013 at 19:52

Sunday, Dec 15, 2013 at 19:52
I have land cruiser dual cab have 800kg springs with 50mm lift
Have done desert trip this year with no issues also got bellows operated from inside the cabin to adjust as needed I never go over 15psi for the above reasons weight 3700 have done GVM upgrade to 3780. I would work on the springs first.
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FollowupID: 804422

Reply By: The Bantam - Sunday, Dec 15, 2013 at 10:17

Sunday, Dec 15, 2013 at 10:17
The first and most important thing to consider is actually how much weight you are carrying.

All too often touring 4wds are actually over weight or over weight on one of the axles, usually the rear.

Then there is the consideration of weight distribution.....that is determined by where the weight is placed on the vehicle.....all too often the weight is too far back.

It is possible to be well and truly under GVM, but well and truly over loaded on the rear axle.

One of the big weight disadvantages on utilities is having spare wheel carriers on the rear of the vehicle.

By the time you fit a wheel carrier and a couple of wheels on the back of the long overhang that exists on most utes, you have shifted rather a lot of weight to the very rear of the vehicle.

Dual cab utes are shockers for shifting too much weight to the rear.

Have you put the vehicle over the scale fully loaded and got an axle split.
You may well find you are carrying more weight on the rear than you thaught.

remember too, all the typical utes carry nearly the entire designed payload on the rear axle..AND the ride height varies a great deal between unladen and fully laden within specification...this is just a fact of life.

Of course if you stiffen the suspension by any means, you will reduce articulation....we need articulation off road...and there is no way arround that.

There have always been cheap options aimed a carrying heavier loads than the factory standard suspensionis designed for.......all too often they have been and are still used to patch up a problem that remains unsolved.

Air adjustable shockes ( like in the 80's) helper springs of various sorts or the current suplimentary airbags......none of them actually solve the problem....most of them have unwanted consequences.

First know how exactly much weight you are carrying and how it is distributed.

If you have too much weight , too far to the rear of the vehicle....there is only one real solution.

cheers
AnswerID: 523089

Reply By: Ozrover - Sunday, Dec 15, 2013 at 10:52

Sunday, Dec 15, 2013 at 10:52
G'day Powernut,

I don't know if you've done it yet but if you haven't then have coil hat supports fitted, GU's are notorious for tearing them off especially with air bags fitted.

It's pretty easy to do with a tray back Ute, but get it done properly & you wont have any problems with them.

Also keep an eye out for bulges in the chassis rails, this means that the cassis is bending there are fixes for this as well.

AnswerID: 523091

Reply By: Member - Ross G5 - Sunday, Dec 15, 2013 at 19:55

Sunday, Dec 15, 2013 at 19:55
Hi I have similar set up try moving one of the spares onto bars on the cabin roof makes a huge difference.
AnswerID: 523128

Follow Up By: Batt's - Sunday, Dec 15, 2013 at 21:04

Sunday, Dec 15, 2013 at 21:04
Hey Ross can I ask how you got the gvm upgrade approved I'm in qld and the motor registry told me that I can't upgrade the gvm of my stretched twin cab GQ. I'm just about to fit 50mm heavy duty springs polyair bags, tough dog adjustable shocks any info would be appreciated Thanks
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FollowupID: 804426

Reply By: Member - Ross G5 - Sunday, Dec 15, 2013 at 21:37

Sunday, Dec 15, 2013 at 21:37
The GVM upgrade is done prior to registration or latter with engineers certificate through arb. Need too replace front and rear springs the gu with airbags is not good as the spring towers will crack have had it happen need to strengthen them first.
AnswerID: 523135

Follow Up By: Batt's - Monday, Dec 16, 2013 at 19:24

Monday, Dec 16, 2013 at 19:24
Mines had polyair bags in since 2006 without a problem I'm putting them back in when I swap the springs over I have heard people have problems with the towers cracking might have something to do with overloading or bashing the vehicle threw rough ground. I might check with arb about a certificate but I'm using tjm springs because I use to work for them and still get a good discount on their gear Thanks
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FollowupID: 804499

Reply By: troopy 47 - Monday, Dec 16, 2013 at 05:09

Monday, Dec 16, 2013 at 05:09
Hi Ross, What springs are you running under the rear my dual cab is set up very similar but my spare are over the rear axle and have jerry can holders on the rear canopy.
I have ARB GVM upgrade with constant 500 kg rear springs, if you 700 kg springs i would be interested to hear how it rides.
Cheers Terry.
AnswerID: 523146

Reply By: Member - powernut (AFL Power) - Monday, Dec 16, 2013 at 08:51

Monday, Dec 16, 2013 at 08:51
Well springs really are a topic of interest. Thanks to all the replies, a lot of well considered advice so thanks for your help fellow 4 x 4 ers.
I should give a bit more back ground to my question. I started with 300 kg progressive EFS coils but after dropping the alloy canopy on realised we needed stiffer springs. So up graded to 500 kg non progressive. Worked well except when fully loaded on what would probably be our biggest trip the CSR.
So back home canopy off, the ride is just ok on good bitumen but around home and on rural tracks it is too stiff. An empty tray top is the other extreme to a full trip set up. So 100 kg of weight on the tray helps but going back to the 300 kg progressive rate coils is a better all round result.
Some advice was given on shifting weight forward. Yes water tank and batteries up the front of the canopy. Spares out back? Agree totally. Too much weight too far back. I might try mags just for the spares and see if that helps.
Overloaded back Axle. Agree totally. I have a weigh bridge on farm and documented every stage of canopy figment and load up. Conclusion. Back axle too far forward, not much we can do there.
So there we have it. Tray tops are more sensitive to stiff springs than wagons. Country roads more sensitive to stiff springs! I just need an option that gives me a reasonable ride empty, but can be boosted when loaded,be it for a short trip home with a ton of fert or loaded on a camping trip? Lots of negatives about air bags of all makes. Maybe we expect too much from them. Remember my question was about using them as helpers.
AnswerID: 523152

Follow Up By: splits - Monday, Dec 16, 2013 at 11:02

Monday, Dec 16, 2013 at 11:02
"Lots of negatives about air bags of all makes. Maybe we expect too much from them"

Not only air bags but the cars as well. Read the link that Nomadic Navara
posted yesterday under my original post. This additional information posted by Collyn yesterday explains it even further. You are playing with fire with these things. Many use them, some get away with it but plenty don't.

Those two spare wheels on the back of your car just on their own could cause a lot of problems with air bags. When the chassis drops on rough surfaces and is brought to a sudden stop by the rapidly hardening bags, they will continue falling generating forces that will increase by the square of the distance that they are behind the bags. The same will happen to everything else behind the bags. Your chassis may already be developing metal fatigue but it may not be visible yet. I have seen cracked Patrol chassis in the rear axle area and they are noted for ripping the top mount for the coils off the chassis. There is a photo of this in the photo gallery section of the Mt Dare Hotel web site.

I think a lot of car owners could save themselves a lot of trouble if they used both of the features of their cars and that is carrying and towing. There is a reason why the Army uses those little number 5 box trailers behind their Land Rovershttp://www.remlr.com/trailer-no5.html They designed them in the 1960s and are still using them. They weigh around 360 kgs and carry 500 kgs. They have a short draw bar and no huge ball weight. If you took 500 kgs out of your car, you would not have a suspension problem. You would be under your carrying limit and you would be miles under your maximum towing capacity. Reliability, especially in places like the Canning, would be at its maximum level.
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FollowupID: 804456

Reply By: troopy 47 - Tuesday, Dec 17, 2013 at 21:12

Tuesday, Dec 17, 2013 at 21:12
I agree airbags might cause problems but from what I can find out so far is with max 30-40 psi there should be no problems at all.
AnswerID: 523230

Follow Up By: splits - Tuesday, Dec 17, 2013 at 23:07

Tuesday, Dec 17, 2013 at 23:07
Where did you get that information from? 30 to 40 psi is more than enough pressure to cause major problems. In your case though, if you are driving a Troopy, the support given to the chassis by the body, may prevent it from bending. You will still be slamming the chassis down onto the hardening bags and sending higher shock loads into the chassis, diff housing, wheel studs and bearings. I have seen cracked chassis, broken diff housings on Landcruisers and plenty of broken wheel studs. Heavier springs are also good at cracking spring hangers.

I have studied all the information that I have been able to find on air bags ever since I bought a cab/chassis 4wd ute seven years ago and became aware of the chassis bending problem. I have saved a few photos off the net of bent chassis cars that clearly show they don't have air bags but I have also noticed that the vast majority of bent chassis cars do have them. When you look at the type of spring they are and how they work, it is easy to see why.

Have a look at the four links below. Read the last post on the thread on the first link. It gives you a good idea of how an air bag works.

The second link lists the qualifications of the man who wrote it. It is hard to argue that he does not know how a spring works.

The third link is an article that he wrote for Caravan and Motorhome magazine. Part of it gives you a brief insight into how complex car suspensions can be. It is not a bad idea to find out exactly how yours works and what you are doing to it before you start changing the design.

The forth link shows a DVD that I bought earlier this year. Stop the short sample DVD on the site at the 15 second point. You will see that the extra cab with the camper has a bent chassis. The car looked ok at the start of their trip along the Gunbarrel Hwy from Giles weather station. The owner added a little more air to its air bags a few hundred ks later. The chassis soon started bending. They removed the camping body and wheels somewhere up near the top of the Gary Hwy. The chassis was kinked badly right at the rear edge of the air bag mounting point. They removed the bags then had to unload a lot of the heavier items in the camper onto a Cruiser ute in the convoy. They were lucky it was only about half loaded. They then drove the car back to Warburton..

I was told later by the people who made that DVD that the camper was left at Warburton and the car was taken back to Qld for repairs. The car was then sold and replaced by a larger ute which was then driven back to Warburton to pick up the camper. That all adds up to a lot of inconvenience and expense then you have the added cost of altering the suspension design in the first place..

This is just another example of buying the wrong car and trying to make it do something that it was not designed to do.

My ute has been driven over a lot of Outback roads, including the Gunbarrel, in stock standard form without any problems at all. I have never had it up to maximum weight let alone overloaded. If I wanted to carry more gear, I would build a little trailer that was no bigger than it had to be.

http://www.caravanersforum.com/viewtopic.php?f=2&t=44107

http://www.caravanandmotorhomebooks.com/about_the_author.html

http://www.caravanandmotorhomebooks.com/pdf/vehicle_dynamics_complete.pdf

http://www.lifestylevideos.com.au/Desert_Highways-dvd.html
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FollowupID: 804559

Reply By: Injected - Friday, Dec 20, 2013 at 09:33

Friday, Dec 20, 2013 at 09:33
One of our travelling companions has a 4.2 GQ with full air bag rear end and Koni shock absorbers.
It was done this way because they have a slide on camper. They slide the legs into camper, let the bags down a bit and drive out from underneath.
Offroad in the rougher stuff its great as he can set the pressures in the bags to suit the load.
Make sure that they are rolling sleeve airbags, as the bellow shaped ones aren't as smooth in operation.
As the vehicle will be fully airbaged rear ( and front if you want) you will need a good shock absorber to control the airbag.
Purchase an aircompressor and in cab controller it will be a brilliant setup.
Regards
AnswerID: 523302

Reply By: Member - powernut (AFL Power) - Friday, Dec 20, 2013 at 11:48

Friday, Dec 20, 2013 at 11:48
At last we are getting some positive comments on personal experience of using air bags.

Re towing a small box trailer to carry the load rather than overload the tow vehicle suspension? That's a good idea except on normal trips I will tow my camper trailer. Trips in more extreme conditions require more gear and trailers are a huge negative. In fact our group thought they should be banned on the CSR as the tow vehicles do a lot of damage to sand hill run ups just trying to pull trailers over them.

So I overloaded for one major trip! Better than running out of fuel or what else you might be short of because you didn't carry it. That's why I bought a GU tray top as it is one of the better, simpler ,read less likely to break vehicles. I did strengthen the rear spring towers, fitted a larger radiator etc, all the things that are reported as suspect on a GU I read about and fixed before leaving home. I didn't break anything. The chassis is still fine, I let the air out of the polly bags to let the suspension do its job, and then pumped them up again to 20 psi when on the black top coming home.

Should I fit my two spares on the back of the canopy to the top front. Or should I replace the rims with mags to cut down on weight over the rear? I think when I have the canopy on next, I will take them off whilst the rear axle is on the weight bridge and check what weight they are adding to that axle before I rush in to any changes. They work well there and look the part.

All I want now is take off the 500Kg non progressive rate cols to fit my 300KG progressive rate coils on the back to improve the empty ride, and either fit the poly bags with a spacer to lift them a little, or fit rubber air bags so I can carry a heavy load occasionally. Shouldn't be too hard should it? I might just be a bit fussy about ride quality and load flexibility but with a truck load of suspension gear on the market surely it is just a matter of seeking advice and trying some options, with out doing silly things.

I think I can get the best of both worlds without shaking the vehicle and my back.

Now the last reply mentioned a different type of air bag, (Sorry I cannot refer to the writers name,). Any chance of a brand name or more specific type.

I appreciate the positive ideas rather than the doom and gloom some of the writers want to pas on. Look I know guys have bent chassis and done all sorts of bad things with air bags, but I don't consider I am in their league if you get my drift. I can read a problem with my vehicle and I can avoid the nasty errors some of you have written about. But hey thanks for contributing, it is for every ones benefit and I understand the warnings are general in nature.

So lets get the rig rite, load up and go out and have some fun away from the phone, work and other modern day hassles. This country was made for touring.
AnswerID: 523306

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