Airbags/air springs for rear ride control and load calculations

[Woodswanderer]

Looking to install an air lift rear kit from Michigan truck springs. Has anyone done an airbag or air load leveling setup on their XJ? Still mostly stock with new oem replacement parts (upgraded to HD/better parts material where possible)

Im trying to also calculate the total load capacity of the setup. MTS says the kit provides 2000lb of load leveling capacity (assuming 100% efficiency, engineering wise its more like 1500-1600lb after 20% loss margin), what i need to find out is if thats additional per spring or pair, or if its total capacity overall in combination with the rest of the suspension per spring/pair.

Specs of rear suspension design are as follows:

-Upgraded rear leaf springs to Husky HD @ 745lb/spring (equivalent to factory upcountry spring rates?)
-moog thermoplastic sway bushings at links
-energy suspensions sway bar mount bushings
-KYB monomax shocks with bar pin flag nuts

-On hand-
Gabriel skyjackers - 90 psi max, cant say what the load rating is at max psi

I may install 1” lift blocks front and rear when i do the Crown HD front springs. Rear KYBs may get pulled too, might be blown (in under 5k miles of highway and town driving).

How can i calculate the overall load capacity of this setup? It cant be as easy as adding up all the numbers and subtracting 20% 🤣


Sent from my iPhone using Tapatalk

[Woodswanderer]

Task 2 of this job: design and install an electopneumatic circuit with gauge for two different pressures. Cant decide between full independent or single circuit. Its a Jeep, not a low rider. Load leveling, not stance.

Having rear air shocks on hand i could plumb two independent, single path circuits into the shocks and airbag springs. Starting with air shocks, run abs tubing back to a T, into another T valve with the sending unit. Airbags get the same setup with the second sending unit. Two switches in cabin.

From there, connections at the pump are what have me thrown off. I want to use a single pump. How? Solenoids and diverter valves with a reservoir tank? Relayed switches? Or just say eff it and run 1 pump per circuit?


Sent from my iPhone using Tapatalk

[Woodswanderer]

Part of me also wants to wire in a pressure switch that will activate the pump when load/squat in the rear is detected. Self leveling suspension...

P2 platform Volvo XC70 wagons had a switch on the rear for self leveling that may work if mounted properly and the armature is modified.


Sent from my iPhone using Tapatalk

[Woodswanderer]

Bumping this up. Picked up a 10gal air tank to use as a reservoir. Has a fitting on top that i can plumb my sensor into. Most likely going to go that route and just rig up the compressor to the airbags in single circuit.

Air shocks will run independent with the valve mounted on the hitch, and OBA connection from the reservoir tank to inflate. Planning to run tools with this setup too (small impact, die grinder, air ratchet) eventually.

Anyone have a good suggestion for an HD compressor that wont break the bank?


Sent from my iPhone using Tapatalk

[sdspearo]

Originally Posted by Woodswanderer

Anyone have a good suggestion for an HD compressor that wont break the bank?

Not sure what they cost now but I've been happy with my Puma 3/4hp (the one with the blue tank).

[sdspearo]

Check out Skruffy's build...

https://www.naxja.org/forum/showthread.php?t=1162234&highlight=skruffy+air+sus pension

[Woodswanderer]

Originally Posted by sdspearo

Check out Skruffy's build...

https://www.naxja.org/forum/showthre...r+sus pension

Thanks. Thats more in depth than i plan to get into. Keeping leaf spring setup in the rear, adding Airlift airbag helpers in place of bump stops is the plan.

Compressor-wise, the Viair was recommended by a buddy of mine that was into TJ stuff. Pricey option and i’d like to find cheaper.

The digital gauge i plan to use comes with 2 sensors in the package, pre-wired. 1/4” npt iirc


Sent from my iPhone using Tapatalk

[Woodswanderer]

https://www.ebay.com/itm/2-Inch-52mm...-127632-2357-0

This is the gauge i plan to use (to match trans oil temp gauge).


Sent from my iPhone using Tapatalk

[Goose_XJ88]

There is also the old GoJeep writeups

http://gojeep.willyshotrod.com/Howto...Suspension.htm

http://gojeep.willyshotrod.com/Howto...Suspension.htm

[Woodswanderer]

Originally Posted by Goose_XJ88

There is also the old GoJeep writeups

http://gojeep.willyshotrod.com/Howto...Suspension.htm

http://gojeep.willyshotrod.com/Howto...Suspension.htm

👆🏻🙏🏻🙏🏻🙏🏻


Sent from my iPhone using Tapatalk

[Skruffy]

Woodswanderer,
I think what you are planning to do will work out well. Much of the advantage of the air springs will be obtained by just using bags and you save the giant hassle and $2700 cost of a coil conversion.
After driving around my XJ with air springs for almost 3 years now I can tell you that air suspensions in general are very forgiving.
When my XJ is at highway height and totally empty it rides great, when I load it up with stuff and it drops 2”, I just put it back in highway height and it rides great. I can hitch my 4000lb trailer to it, it sags of course, then I just fill the air springs back to highway height and it rides great.
I think the amount of weight that it would take to max out the Air springs would have long since crushed the chassis.
I say go for man. Air suspension is so much more adaptable for any situation that your XJ can be in.

[Woodswanderer]

Originally Posted by Skruffy

Woodswanderer,
I think what you are planning to do will work out well. Much of the advantage of the air springs will be obtained by just using bags and you save the giant hassle and $2700 cost of a coil conversion.
After driving around my XJ with air springs for almost 3 years now I can tell you that air suspensions in general are very forgiving.
When my XJ is at highway height and totally empty it rides great, when I load it up with stuff and it drops 2”, I just put it back in highway height and it rides great. I can hitch my 4000lb trailer to it, it sags of course, then I just fill the air springs back to highway height and it rides great.
I think the amount of weight that it would take to max out the Air springs would have long since crushed the chassis.
I say go for man. Air suspension is so much more adaptable for any situation that your XJ can be in.

You just basically sold me 😅 planning to pull a 4000lb-4500lb 26’ travel trailer (with load distro and electric brakes). And i’m a cheap mfer, $220 for air springs is still a lot better than $2700 lol. I can do a lot more than just airbags towards that towing goal with $2700 invested (disc brake swap/upgrades, 1 ton steering, 2” lift)

Maybe if i hit the lottery one day i’ll build up an XJ proper...or just go buy an SJ grand wagoneer and drop a newer pushrod V8 into it 🤣


Sent from my iPhone using Tapatalk

[Skruffy]

Glad to hear it
Towing 4000lbs with an XJ is not for the faint of heart. Having working breaks in the trailer is absolutely needed. Upgraded brakes on the Jeep are needed too if you have bigger tires. I’m running 35’s on TJ rubicon axles. I couldn’t lock up the front brakes until I did the VANCO upgrade.
My chassis was rated to tow 5000lbs but that seems like a fantasy even after the engine swap.

[Woodswanderer]

Originally Posted by Skruffy

Glad to hear it
Towing 4000lbs with an XJ is not for the faint of heart. Having working breaks in the trailer is absolutely needed. Upgraded brakes on the Jeep are needed too if you have bigger tires. I’m running 35’s on TJ rubicon axles. I couldn’t lock up the front brakes until I did the VANCO upgrade.
My chassis was rated to tow 5000lbs but that seems like a fantasy even after the engine swap.

Its not going to be an all the time thing. Planning to do the WJ front brakes, ZJ rear discs, fully worked suspension on 2” lift with nokian 235/75-15 e load index tires. Reese towing hardware rated to 5500lb. Pretty sure i’ll be running in full time 4wd too to pull this much.

Door tag says im rated to 4900lb capacity in stock form on 215/75-15 tires...thats a huge stretch imho.

Really only need to be able to move the trailer to land and occasionally off the land. The 4.0 while being a great engine is a bit underpowered for that much weight and i’d be much better served with a v8 swap (but that kills half the fun and takes the reliability of the 4.0 out of the equation...this is still a daily driver first and foremost)

[Skruffy]

Go for it man. Put the build on here I am real interested to see how it works out.