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Air over leaf - anyone using it?

burntkat

NAXJA Member #1145
Location
Charleston, SC
I'm wondering if anyone has used an airbag over leaf spring setup either as a supplement to the springs (enabling a plush ride daily, and a good load support when trailering or hauling) or as the primary spring after removing all but the main leaf?

I'm looking to do this for my S truck owing to the spring rate being super soft (and I don't want to fool around with custom springs), and as an adjunct I am thinking it would be quite suitable in my XJ for expo use.
 
You just need a good set of leafs and shocks to get a plush ride and still have enough support to haul. Removing leafs will only lead to horrible axle wrap if you don't have a anti-wrap/traction bar.

Having said this, someone(can't remember who) makes a long travel air bag kit that allows the the axle or the chassis to separate from the air bag. Most air bags attach to both the axle and the frame, which isn't exactly what you want.

EDIT: It's daystar that makes a poly bag cradle...

images.ashx


Either way, you don't want the air bags to be supporting the majority of vehicle's weight. They should only be adding to the spring to help support loads and level the chassis.
 
Why do you say this? There are plenty of vehicles out there with air-only suspension.

I'm not arguing, just curious.

EDIT to add: thanks for the additional info about the cradles- you answered a question I was beginning to ponder. This makes selection of the bags for my truck MUCH easier.
 
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Why do you say this? There are plenty of vehicles out there with air-only suspension.

I'm not arguing, just curious.

EDIT to add: thanks for the additional info about the cradles- you answered a question I was beginning to ponder. This makes selection of the bags for my truck MUCH easier.

Yes but not with leafs. They would typical be a a arm type set up and IFS vs solid axle.

To go back to your main question, my dad runs them on his trucks for heavy loads and loves them.
 
I have them on my work truck (service body--heavily loaded) and they are a great solution for that situation.

CoachBruce runs them on his XJ and is happy with them. I have toyed with the idea. I will have to look into that Daystar cradle.

With my work truck I have appreciated the ability to adjust the ride in order to cope with heavy loads, and even a couple of times have taken advantage of the ability to lower to bed for the sake of loading/unloading heavy or otherwise awkward loads.

I do think the ability to adjust the pressure with the flick of a switch is worth it. I would not want to have to use an air chuck every time I needed to add air. And it will be necessary to add air several times a year just to keep things at a normal pressure.
 
Why do you say this? There are plenty of vehicles out there with air-only suspension.

I'm not arguing, just curious.

EDIT to add: thanks for the additional info about the cradles- you answered a question I was beginning to ponder. This makes selection of the bags for my truck MUCH easier.

I think gojeep had a write up a long time ago about air bags.i like the cradle idea for an off road Jeep too.

But yea one main leaf would leave your axle flopping all over the place, plus that bag really isn't builtfor being the sole spring component, but I'm sure you could find some out there. I used to see bag conversions on f450-550s. They all had 4 links. I think the biggest thing you would need to run a bag only on an xj is frame reinforcement. I do not believe the factory rail could take that kind of load concentrated to a small area like that. And keep in mind an air bag that could fit there has a very small amount of travel, which is why most factory airbag suspensions have the bag mounted to the side to increase the height of the bag and also fold into itself.
 
I think gojeep had a write up a long time ago about air bags.i like the cradle idea for an off road Jeep too.

But yea one main leaf would leave your axle flopping all over the place, plus that bag really isn't builtfor being the sole spring component, but I'm sure you could find some out there. I used to see bag conversions on f450-550s. They all had 4 links. I think the biggest thing you would need to run a bag only on an xj is frame reinforcement. I do not believe the factory rail could take that kind of load concentrated to a small area like that. And keep in mind an air bag that could fit there has a very small amount of travel, which is why most factory airbag suspensions have the bag mounted to the side to increase the height of the bag and also fold into itself.

Running a leaf spring, the load is in 2 small areas...where the front bolts to the frame and where the shackle bolts to the frame....I don't see a difference really in those 2 relatively small points vs 1 much larger point for an air bag.

I do agree most air bags are designed to supplement the suspension...not become it.
 
Yes, but it was directed to running an airbag only, like if there was no spring and the airbag was the only source of "spring" to hold the rear up. I agree if the air bag was used as a supplement it would be ok. That's what I meant by running a. Bag only. Or maybe that's what you meant?

My other argument would be where the loads are concentrated. The mounts of the leafs are spread over a large area, distance wise. And the the rear shackle mount is close to the hitch. If you only had a bag and were towing, there's a lot more leverage for the frame to deform because of the distance in the bag mounting compared to the hitch location. Or am I crazy?

My frame started deforming after the whacking the bump stops a few times tho so maybe I just don't trust them to be exactly strong.
 
Yes, but it was directed to running an airbag only, like if there was no spring and the airbag was the only source of "spring" to hold the rear up. I agree if the air bag was used as a supplement it would be ok. That's what I meant by running a. Bag only. Or maybe that's what you meant?

My other argument would be where the loads are concentrated. The mounts of the leafs are spread over a large area, distance wise. And the the rear shackle mount is close to the hitch. If you only had a bag and were towing, there's a lot more leverage for the frame to deform because of the distance in the bag mounting compared to the hitch location. Or am I crazy?

My frame started deforming after the whacking the bump stops a few times tho so maybe I just don't trust them to be exactly strong.

agreed..on most points.

yes the leaf spring mounts are spread over a large area to give strength in so far as keeping the suspension under the jeep, but as to punching thru the frame or deforming it, but they act as point loads

and I did mean the air bag alone may have roughly the same area as both the front & rear mounts combined...depending on the diameter of the bag & its mount.

yes, the bag would have much more leverage to bend these weak @?? frames with.....

mine cracked & deformed from a cargo carrier hanging off the back...granted, it had a deer on it a few times, and I was not driving slow or being easy on the bumps.


.
 
Are there more information on those air bags? i.e. the compressed and extended length? IMO, they could be a great alternative to the present rubber bump stop.

To supplement the load carrying capability of the existing leafs, some frame re-enforcement is necessary. For airbags to be the sole load bearing equipment on the XJ in it's current design, one would have to at least triangulate/four link the axle to keep it under the vehicle.
 
No, one would not have to 4link the vehicle. There are plenty of vehicles running air over leafs.
 
Are there more information on those air bags? i.e. the compressed and extended length? IMO, they could be a great alternative to the present rubber bump stop.

Size depends on the unit. I found some 2500 series on Amazon that are 2.8 collapsed, 10 inflated, 6 inch diameter. These are $80 shipped for a pair. Good enough for a proof. Of concept and rather cheap as well. I'm going to put them front and rear on my S10 as it's got a very soft suspension, and I want the flexibility of air over leafs. If that goes well, I will be doing a pair out back on my XJ, after a frame reinforcement.

What got me started down this road was the need to bumpstop several of my builds. I considered sumosprings, and given that they are a retrofit for airbags, a light went off.
 
No, one would not have to 4link the vehicle. There are plenty of vehicles running air over leafs.

Yea, correct,.... if a full compliment of leaf springs are retained. The leafs are what will keep the axle in place and properly located under the XJ or other vehicle. Vehicles and / or trailers that run air bags only to support the load have some metallic mechanical device that keep their axles whether they are the drive axles (see the 18 wheeler tow truck) or the trailers they pull, they all have a locating device to keep the axle under them while at the same time allows the axles to move up and down as necessary.

Those tow rigs I have looked at have what look like half springs attached to each side of the chassis and end at the connection point of the axle. These keep the axle in place forward to backward. They also have a massive panhard rod attached to the chassis similar to our XJ front axle and to the axle which keep the axle properly located axle left to right.
 
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Size depends on the unit. I found some 2500 series on Amazon that are 2.8 collapsed, 10 inflated, 6 inch diameter. These are $80 shipped for a pair. Good enough for a proof. Of concept and rather cheap as well. I'm going to put them front and rear on my S10 as it's got a very soft suspension, and I want the flexibility of air over leafs. If that goes well, I will be doing a pair out back on my XJ, after a frame reinforcement.

What got me started down this road was the need to bumpstop several of my builds. I considered sumosprings, and given that they are a retrofit for airbags, a light went off.

10" sound a bit long but I do not know the S10 except when I see the badge on the fender that indicates it is an S10.

My thoughts are on the XJ rear in which case my thoughts would be more like 4" to 6" to act as a bump stop or help with a heavy load. Even then I am not seeing the complete picture.
 
These are air springs. NOT bump stops. That said, there are some available with bump stops inside them- if you want to pay $200 for a spring. Nope!

I know something has to be under the vehicle to keep the axle in place (DUH?). But my point is that there are people running stripped down leafs (removing all but the main and maybe two longest) which does that job, and air springs doing the heavy lifting (literally). An antiwrap bar would of course be a good idea for us in the offroad community if doing that. Maylbe a panhard as well, if we are seeking the best of both worlds (and I am).

10 inches is definitely a tall bag. There are different bags available (rolling lobe, convoluted, etc). I went with these because they suit my build- my SAS S10 is at something like 11" of lift from a factory truck (I've got SOA front/rear, Dana 44s, etc). A lot of tlhis can be addressed with bracket locations. I want to run the cradles posted above so went with the 6" round double convoluted bags, as I have something like 18" of wheel travel. My build is very softly-sprung, I basically built it as an expo rig with DD in mind. I can nearly max out my 5' hilift jack before I get a wheel off the ground (which is why I mainly use bottle jacks when needing to do a tire change, but that gets into another discussion).

(EDIT: on new computer, lost part of the post..)

I'm investigating the impact of line size on fill rates- the bags I ordered have 1/2" fill ports, and I understand some people are able to make the vehicle jump off the ground when using 1/2" line. NOT what I'm after. I want to be able to adjust ride height on the fly given different parameters- so I can kneel the truck when parked to make it easier to get into, or load the roof rack. Don't need to lay frame, and that would be rather impossible with a solid axle vehicle anyway. I'd like to have it drop a couple inches (low clearance, small deflection for steering)when driving on the interstate, or going to maximum height needed when doing parking lot maneuvers (slow speed, high deflection of steering). To do so I'd need the ability to move across about a 6" range of height in 2 seconds or so. This would be a future upgrade, for now I want to get the bags in hand and scope out mounts fore/aft to stiffen up my spring rate. I am getting rather alarming body roll (better addressed with a swaybar, but that won't do all of it) and excessive front end dive under braking (definitely comes down to weight/spring rate). I added a 5/7L V8 where a 4.3L V6 used to live- difference is something like 100 pounds, IIRC. I will also be adding a heavy front bumper, winch, and hilift up front. I could get with any of a number of custom spring shops, weigh the corners of my truck, and hope for the best.. for probably $400/corner. I can put $1500 into the springs, or a couple hundred into supplemental air springs and gain more features. This is why I'm doing the air springs.

First stage of the job will be checking for clearance and fabricating bracketry, installing the springs as supplemental, "dumb" units with an external air fill. Then in the future I will look at going with onboard air (likely a ViAir compressor, with the sliders as tanks), 4 valves (fill and dump for front and rear), stripped down leafs to investigate the ability to control height. After that, it gets into an imbedded controller, probably built on a RaspBerry PI.
 
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And again, it's simply a matter of building an antiwrap bar. I've said that a few times now, and it's NOT a big deal. I built my own suspension here, that's simple. Moving on..
 
18" of travel sounds like a lot,.....but what do I know. My XJ have 10" shocks on the front and uses just about all of it and 8" out back but uses only maybe 6". I have not tried to measure the total travel at the wheel/hub center.

It seem you have a good idea of what you want to accomplish and the best approach that will get you there. I will follow your build and offer my inexperienced comments. :gag:

I like the idea of blazing your own trail instead of following the same old beaten path.
 
Not that it is apples to apples, but my Camaro has mono-leaf springs in the rear. There is a way to do it.
 
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