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Thinking of air bags

DrMoab

DrMoab

NAXJA Forum User
Location
The Utah Backwater
Seems that lately I have been doing more and more back country wheeling with lots of weight hanging off the back and on the roof of the XJ. I am running very soft springs and love the way they work off road and really don't want to mess with them so...l am thinking of air bags.

A couple of questions to anyone who knows.

Is there any reason that setting up airbags with a custom mount closer to the center of the axle would be a bad idea? My thoughts are if they were closer together then when the axle articulates they would not have to move as far...hense you could use shorter airbags.

Two...If you hook airbags together with one bigger air line running between the two wouldn't this also keep them articulating by transfering air between the two bags?

I am not looking to lift my jeep anymore...Just keep it level with a lot of extra weight.
 
Dad ran airshocks on his '88 and '90 (and we've since installed them on my sister's '92 and my '98) and wheeled his as well as lots (and lots and lots) of highway miles and ran 235/75/15's on them as well (the '92 and '98 will be getting some before summers out too) and had them work well in most cases. We have noticed that if youp have alot of weight behind the rear axle and seat the whole truck will gain some height instead of just the rear. Dad had about 500lbs of railroad related equipment and tools in both his for years, where my sister and I have mainly used them for carrying cargo for short distances and I've used them on family road trips where it's all four uf us and our luggage.
 
DrMoab said:
Is there any reason that setting up airbags with a custom mount closer to the center of the axle would be a bad idea? My thoughts are if they were closer together then when the axle articulates they would not have to move as far...hense you could use shorter airbags.
Click to expand...

The problem with this that i see with doing this is that the weight will now be mainly on the airbags which are closer together, this makes the main springs act more like outriggers than actual springs. I would think this would make it unstable.

DrMoab said:
Two...If you hook airbags together with one bigger air line running between the two wouldn't this also keep them articulating by transfering air between the two bags?

I am not looking to lift my jeep anymore...Just keep it level with a lot of extra weight.
Click to expand...

You could hook both airbags together, but i would make sure you have proper bumpstops so that the bags do not compress more than there supposed too, also don't use the bellows style bag not enough travel. instead use the type that rolls over a steel center (i forgot the name of them at the moment)

If you do this lets us know how it turns out.

Dingo
 
DrMoab said:
Is there any reason that setting up airbags with a custom mount closer to the center of the axle would be a bad idea? My thoughts are if they were closer together then when the axle articulates they would not have to move as far...hense you could use shorter airbags.

Two...If you hook airbags together with one bigger air line running between the two wouldn't this also keep them articulating by transfering air between the two bags?

I am not looking to lift my jeep anymore...Just keep it level with a lot of extra weight.
Click to expand...

You'll have to be concerned with full droop of the axle as well as when you're articulating, so placing the bags closer together to better handle articulation won't really work. The bags just need to be long enough or they will rip apart after a number of cycles of full axle droop. There are plenty of situations when you get full droop.

Yes, if the bags are tied together it could help articulation, and would sort of artificially increase the spring rate on the down side and decrease the spring rate of the up side. However, I think you're looking for stability when loaded down with camping gear, and the only way to do that is to keep the bags seperate. If load capacity is the only thing you're after, tying the bags together would work, but not as well as if they were seperate. When each bag works seperately, it will basically increase the spring rate to compensate for the load and bring you back to your desired ride height, and will resist swaying.

Finding a bag that is long enough isn't easy, I thought quite a bit about doing the same thing and have looked through plenty of air spring catalogs. I would have done it one of two ways. One idea was to place the bags in front of the spring plate, on the front half of the springs,, using a bottom mount that bolted under the spring plate, so that the bags where in a position where the distance was shorter between full stuff and full droop. The other idea was to make an arm that went from the top of the spring plate to the front of the rear spring hanger, mounted at the spring plate with a rod end and at the spring hanger with a bushing, then mount the air bag on top of that arm. This would allow the use of a much shorter bellows type bag and the rod end at the front mount would allow the suspension to travel freely. I don't remember exactly why I never did that, I still like the idea.
 
I have often thought of this too. I would place the bags on the outter most part of the axle though or it won't have much leverage either way. You could also do a trailing arm setup and put the bags on the arms more forward to give it a somewhat cantilever setup. And as far as what bags to use, there are several. They do make some rather large ones meant for semi trucks that work well. They just take a lot of air. Most minitrucks, or even bagged full size trucks, use a 2500 or 2600 pound bag. I have 2500's in my Mazda and they give about 8-10 inches of lift. A kittle more in the rear because I'm on a cantilever setup. But I have a friend running 3500 pound bags (smaller semi bags) in his S10 and he gets well over a foot of lift. He is able to lay out on 20's and lift high enough over them to turn lock to lock.

As far as hooking them together with one line and just 2 valves I think that would be the best. It would allow for the most articulation as when one bag needs to compress it will push air into the other bag to extend it. It will kind of do everything on its own. The other way to hook them up would be to do them independantly and put a pair of valves on each bag. Downside is it won't transfer air on its own but would give you full control of how much air/extension/compresion is allowed on each corner. You could simply put a pressure gauge on each corner and have a decent idea of what tire is giving you most traction.

And you will want limiting straps as bags aren't designed to hang. In fact that tends to kill them rather quickly either by stressing them out or simply pulling the studs out of the top or bottom as they are just pressed in.

One of the big downsides is that air bags puncture. And it really doesn't take much to render one garbage so just keep that in mind also.

And just for kicks, here is a pic of my project Mazda. 2.5" body drop (channelled frame), custom 3 link rear suspension, bags on trailing arms, all 1/2" line, 1/2" electric valves, Viair 450c compressor, 7 gallon air tank, adjustable pressure switch, and dual needle pressure gauge.

mazdabagged05.jpg
 
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If you are really serious about doing it , I can put you in touch with a buddy of mine who's building a buggy on bags. He researched it for several years and a lot of different bag companies and air systems. Also have a buddy who's been running them on a late model Doodge ram , 4 linked front and rear. He has 14" of ride adjustment in his and has wheeled it everywhere, it's simple and it works. Also with you can force articulation which it very nice in off camber situations.
 
To add to BIGWOODY's post, if you are going to try it yourself or anything don't be afraid to go to minitruckin websites for basic advice or to order parts. suicidedoors.com has been one of the best priced places around for parts. Might not find the huge bags and such but I bet they can help ya out finding it.

I don't know a whole lot about adding bags to a lifted vehicle but have seen it done and know that air suspension is improving by leaps and bounds. So it is definatly something that can be the next big thing in off roading. I know in the last several years it has all but replaced nasty hydraulics in the minitruck/sport truck world. And I know for road racing/autocrossing air ride is the superior way to go about things, there just aren't a lot of companies doing the R & D just yet but its making its way in.
 
I've seen quad convoluted also. Should be plenty of travel :D

"Triple Bellow" 1/2" Port 2-Ply Air Spring
2800lbs rated - 5" Collapsed Ht., 22" Max Extended Ht.
Factory Max Air Pressure - 120 PSI :eek:


conti_3bellow_12_2ply.jpg


http://www.macsspring.com/website/contitech_mainsite.htm

What your trying to accomplish isn't that easy.

1. One bag in the center has a couple of problems.
a. You still need a bag that will handle the verticle travel of the axle. I run about 10" and I bet you are close to the same.
b. By inflating that bag you are basically unloading the springs on the outter end. You still have the weight up above but normally the springs compressed would be providing a higher spring rate. Since they don't it causes a good deal of wobble.

2. Any of the larger bags that have the travel usually have a 2500 lb capcity and a 5 psi min pressure. Since the volume is usually trapped in the bag and they are made not to expand they spring rate goes up drastically with compression. On my F-150 empty and 5 psi in the bags I still got about 1/2" lift and a harsher ride. Larger bags will reduce that effect some but your running a much lighter rig to begin with. You better have some pretty light main leafs and then a good way to control the spring wrap.

The only way I could see it worth while is with a well designed link suspension. If you do that you might as well shoot for more travel than you have now which ends up being a larger bag yet. With the larger bags a dedicated tank is almost required to increase the percieved volume at the bag. This provides a slower compression of the air and a more consistant spring rate. Since you've gone that far you might as well move the bags onto the links which would require a shorter bag and lessens the need for the extra tanks. That would be what I would shoot for. There is that company that makes the kit for the TJ but it's still only a 9" travel bag. I looked into those but didn't want to sacrafice travel for more bling.

I run the cheapo air lift bags inside my rear coils (500# per bag rating). Since the spring rate was soft to begin with they do a pretty good job for what I need right now. In two years I've pulled the line off each bag once and when filled they like to destroy shocks because of the rebound (testing accident :D ).

Anyways, just a little info. It's beer time for me.
 
FWIW, an old friend of mine ran a single 12" Firestone bag on the top of his rear diff for adjsutable carrying capacity and height. I think it was a double-bellow style bag. It worked quite well from what I saw. This was his rig:

moab99goose2.jpg
 
Twistedimg said:
One of the big downsides is that air bags puncture. And it really doesn't take much to render one garbage so just keep that in mind also.
Click to expand...
What type of bag?

There's a ton of TJs, a XJ and even a ZJ here that run OROs AiRock suspension. I've wheeled with all of them and none of them have ever had an air bag fail. I've never heard of one of his bags getting punctured. The XJ had a rear bracket come loose last summer and it shifted everthing a few inches to the side and the airbags were fine.

I'm pretty sure ORO uses a Firestone bag.
 
Goatman said:
Yes, if the bags are tied together it could help articulation, and would sort of artificially increase the spring rate on the down side and decrease the spring rate of the up side. However, I think you're looking for stability when loaded down with camping gear, and the only way to do that is to keep the bags seperate. If load capacity is the only thing you're after, tying the bags together would work, but not as well as if they were seperate. When each bag works seperately, it will basically increase the spring rate to compensate for the load and bring you back to your desired ride height, and will resist swaying.
Click to expand...
One reason I am thinking of doing this is because I work with semis and have access to all kinds of air valves, switches and the sort.

One thing I have thought about doing...Although this would take some figuring out..is to set up some kind of valve that would shut off air from going between the bags...For example.. When you were off road and wanted articulation you could throw the switch and it would allow air to freely go between the bags. Throw the switch the other way and it would close off the line between the bags and act as a stabilizer for the highway.

If you needed to add air or let air out all you would need to do is open the valve...so both bags would equilize, set your pressure and close the valve again.

Clear as mud or am I leaving something out?
 
Lincoln said:
What your trying to accomplish isn't that easy.

1. One bag in the center has a couple of problems.
a. You still need a bag that will handle the verticle travel of the axle. I run about 10" and I bet you are close to the same.
b. By inflating that bag you are basically unloading the springs on the outter end. You still have the weight up above but normally the springs compressed would be providing a higher spring rate. Since they don't it causes a good deal of wobble.

2. Any of the larger bags that have the travel usually have a 2500 lb capcity and a 5 psi min pressure. Since the volume is usually trapped in the bag and they are made not to expand they spring rate goes up drastically with compression. On my F-150 empty and 5 psi in the bags I still got about 1/2" lift and a harsher ride. Larger bags will reduce that effect some but your running a much lighter rig to begin with. You better have some pretty light main leafs and then a good way to control the spring wrap.

The only way I could see it worth while is with a well designed link suspension. If you do that you might as well shoot for more travel than you have now which ends up being a larger bag yet. With the larger bags a dedicated tank is almost required to increase the percieved volume at the bag. This provides a slower compression of the air and a more consistant spring rate. Since you've gone that far you might as well move the bags onto the links which would require a shorter bag and lessens the need for the extra tanks. That would be what I would shoot for. There is that company that makes the kit for the TJ but it's still only a 9" travel bag. I looked into those but didn't want to sacrafice travel for more bling.

I run the cheapo air lift bags inside my rear coils (500# per bag rating). Since the spring rate was soft to begin with they do a pretty good job for what I need right now. In two years I've pulled the line off each bag once and when filled they like to destroy shocks because of the rebound (testing accident :D ).

Anyways, just a little info. It's beer time for me.
Click to expand...
Remember though...I am not trying to gain lift or anything by doing this. The problem I have is I do have a very soft set of springs in the rear...which I love for regular wheeling. The problem with those leafs are when I load my jeep up....which I only do for longer trips it looses about three inches in the back.

The way I want to set it up is that the air bags are completly open to outside air when I don't need them. Maybe set up a valve that opens the line to outside air when I don't need them.

With 600-700 Lbs of gear I just want it to sit level both on the highway and off road.

We are doing a 300 mile jeep-road trip from Lake Powell to Moab right before Fall Fling which will take five days to do...This is more then my currant spring set up can handle.
 
so you just need them to be attached at the top to the frame and have a surface for them to ride on while at static height. Also make sure your setup not to pinch the bags as the axle stuffs. This way with the bags at minimum inflation you should be able to get full stuff, and full extension. When inflated and loaded up they will sit on the axles and support the wieght.

Did I explain that ok? Does it make sense?

Ive also had air bags on the mind off and on for about 3 years now.....started with my yj.
 
fordtech said:
so you just need them to be attached at the top to the frame and have a surface for them to ride on while at static height. Also make sure your setup not to pinch the bags as the axle stuffs. This way with the bags at minimum inflation you should be able to get full stuff, and full extension. When inflated and loaded up they will sit on the axles and support the wieght.

Did I explain that ok? Does it make sense?

Ive also had air bags on the mind off and on for about 3 years now.....started with my yj.
Click to expand...
Yeah it makes sence...I actually understand how they work and what they will do. My biggest questions are about articulation and the best way to keep it and stability at the same time (yeah I know....cake and eat it too :) )
 
Sounds like you have a plan but you need to keep the minimum pressure in the bag. I've replaced several (Firestone and Airlift) that were under inflated. I think the pinches itself (end plates maybe) when they don't have the minimum in it.

Something to try.

1. Get some bags from Off Road Only or find out what they are running. Their bags are the sleeve style bag instead of the bellow style. They are a smaller diameter so mounting is a little easier and I believe they handle right around 10" of travel from compressed to extended height. I think I remember them being a 1500 lb bag.

2. Mount them inward of your stock springs just enough they bag won't rub on anything during compression.

3. Pull one leaf out of your current pack. That should lower the spring rate enough that at the min pressure they rate should be about the same as you currently have. You didn't say if you were running a traction bar but if your springs are already plush I assume you are, removing the leaf will make it more important.

4. Make sure your shocks have better than normal rebound control. Even on the road loaded it will fill bouncy bouncy.

5. Almost forgot. Use a 1/4" valve on the large side. Anything bigger is kind of a pain because of how quick they fill the bag. I like my 1/8" valves with 3/16" line.

With the above I wouldn't bother with a valve for a cross over. The bags will be mounted inward articulation would be the same and maybe a little better on the down side because of the softer leaf pack. With as much gear as your hauling you could tune the spring rate pretty close to what you have now loaded. It won't handle quite as good (more weight) but it would be better than without them.

My bump stop is in the center of the coil. I just cut about 1.5" off the stop and still get the full compression I had before. The coil insert bags I run won't really run the rate high enough to affect that but they do increase the rate quite a bit.

I kind of sounded like I was steering you away when I meant to just bring up some points. Yours would be more difficult than mine just because they have to be retained at both ends. The idea of leaving one end uncaptured might work but with a long travel bag they would want to fold over. Use a double convoluted bag that is just long enough to handle the compression from ride height. The diameter always killed the idea for me. 5-7".

Here are a couple of pics of what I have, mostly for those watching and wondering since they don't really apply to yours:
airbag_1sm.jpg

valves3-sm.jpg

Also mine since mine are low pressure I ran a fairly soft line from the bag to the frame. The coil smashes the line on compression.
 
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