Suspension Upgrades: Round 3 – Rear Adjustable Air-Springs

Ever since the very first day of the 2015 No Highways Tour I have been plagued with rear suspension issues.  This is partly because the LJ is 15″ longer than a base TJ. This increase in length translates into an increase in base weight.  15″ more frame. 15″ more body. 15″ more hard-top.  Ounces become pounds really quick.

Although some do, these air-springs do not replace the coil springs.
Rather these springs go inside the coil springs to act as an adjustable helper-spring.
This is a great option for overland rigs that see dual duty as a daily driver (light load) and an adventure rig (heavy load).
As a bonus, if you’re rig is equipped with onboard air, you can adjust as needed just like you would  your tire pressure.

On top of the base weight of the LJ being higher, as an overlander I am guilty of overpacking.  I always overpack. It’s a very bad habit.  I grew up a Boy Scout so I live by the mantra “Be Prepared.”  As such I always seem to justify extra gear and more often than naught it goes unused.  I still bring it though… you know… just in case.  This has lead to sagging springs both when I was running the stock springs (2015-2016) and the JKS JSpec 2″ lift springs (2016-current).  To compensate for the sag Jim, my de-fact-o “crew chief” suggested air-springs to assist the Jeep’s coil springs.  Time for another upgrade…

First things first, getting the Jeep into the garage and ready to go up on the lift.

The basic kit comes with everything you need to install the air-spring and inflate them manually
If you don’t have onboard air you can purchase an add-on kit that has a compressor and control switches
Eventually I will be adding the switches and solenoids to my current OBA system, but that is another article for another day

One of the first things we did was mock up the airbags before removing the spring

The directions recommend the removal of the rubber bump-stop.  Given the JKS JSpec springs are rated to be 2″ taller than stock we opted the leave the bump-stop in there.  Since this is contrary to the directions I cannot recommend this as a standard practice.  Both Jim and I do not make such decisions easily.  Luckily he has a history running air-springs on his trucks and trailers and after mocking things up this was a reasonable conclusion we came to.  This is often the case when installing aftermarket parts that are designed for stock parts when you already have other aftermarket parts.

With the spring out (which wasn’t easy) it was time to drill

The airbags are oriented with the bag nipple down
This routes the air-line up through the center of the spring perch
After drilling a small pilot hole a step bit was used to enlarge the hole

We used a bit of gasket maker and a rubber grommet to protect the air line
Neither was included with the kit not even mentioned in the directions
This was just some extra stuff we had laying around
Suggestion: Do this AFTER you put the spring back in

The large rubber isolator is what is included in the kit to protect the underside of the air spring and the air line
There was nothing to hold it in place so we opted for a few zip-ties

Once everything was in place, including routing of the air lines, the bags were inflated to test for leaks

The fill-valve was mounted on the rear bumper
This is temporary until I can save up and buy the parts necessary to tap into my OBA system.
Since the chuck for my OBA is in the rear of the jeep, this won’t be too inconvenient.


In hindsight this should have been the very first modification I made to the LJ.  If you have a stock 4×4 you’re looking at taking overlanding, I’d highly suggest air-springs to help with the load.  I know a number of other people running them on Tacomas, Jeeps, full-size trucks, and smaller SUVs.

The kit was inexpensive (under $100 for the Jeep specific kit, other kits might be pricer for different/larger vehicles) and super easy to install.  The kit can be found on the eTrailer website.  They also have a great step-by-step installation video with some before/after comparison shots on their YouTube.  Although the instructions included in the kit were helpful, the video was hands down what helped the most.  Didn’t hurt their did the install on a silver ’04 LJ either.

I haven’t had too many chances to dial in the air pressure for the air-springs just yet.  Already, with only 10 psi of air, the ride was noticeably firmer.  However, as you can tell from some of the photos if you have a keen eye, I have two blown rear shocks (again). This is no fault of JKS or their quality.  I did some post NHT measurements and even with the 2″ lift springs the LJ was running with 1″ of sag compared to stock.  Once I took everything out the ride-height leveled out.  So yeah, I’m running a bit overloaded.  The trailer certainly doesn’t help either.  This was the main reason for going with air-springs rather than heavier rated springs at this point.  The JKS kit does ride amazingly well and if I wasn’t fully-loaded with overland gear and wasn’t running the larger 31.5 gallon GenRight tank I think the JSpec springs would be good as-is.  However, the combination of the LJ’s length, plus my tendency to overpack, and the extra fuel just means it’s way beyond what the JKS springs were ever intended to handle.

Once I get some new shocks installed I will be doing some more measurements and some trial-and-error to dial in what pressure I need to run in the air-springs. As such, I’m sure I’ll release a more detailed look at suspension heights.  So stay turned.


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