let me start by saying that I have zero experience with IRO.
i'm always weary of companies that still supply drop pitman arms with some of their lifts for TJ's. they have been known to be a bad idea for almost 20 years.
it looks like their LJ specific kits are all long arm kits which incorporates a skid for ease of installation, generally means they sacrificed geometry and the offroad abilities will be diminished. almost all of the long arm kits are downgrades for this exact reason, especially the mostly bolt on ones.
I'd be very weary of their control arms. both the joints and the no jam nut, threaded clamping terminals design.
sadly suspension geometry and its effect on ride characteristics is not a short conversation. you can google anti-squat, anti-dive, and roll center to gain a grasp of how a 4 link suspension works. here is a decent break down of how they affect ride but the amount of actual data could fill a full college program. https://www.crawlpedia.com/4_link_suspension.htm
as to how long arms are not ideal on TJ/LJ's just google long arm tj lj. there will be tons of threads on this forum and others talking about pros and cons. many people come in thinking they will be a huge upgrade and once they learn of the drawbacks they realize they arent all they are advertised to be. the craziest thing for most to grasp is that it isnt the arm length itself, its the mount locations that matter.
now if you have a good understanding of suspension geometry, have solid fab skills, and the tools to make your own or install a kit like Savvy's mid-arm, then going away from short arms may be beneficial.
I'm no engineer and dont wanna pretend that I know a lot. Before jeeping, I was into RC car racing, shifter carts, drag racing and lowriders. I know just about enough to get lucky and sound smart, or sound foolish.
I dont wanna turn this thread into what's better, long, mid, or short arms. That would have the potential to go nowhere fast, except possibly in the gutter.
The first drag car I put together was a 69 Chevelle. Initially I built it with an adjustable ladder bar that was tied into a driveshaft loop. It did well for me, but I swapped it out for a full 4-link. Fast forward to more recently, I'm working on a chevy obs dually, bagged and bodied. The rear suspension on it is a wishbone style 3-link. The common denominator between the two above mentioned examples, and everything I've had between those two, is that the rear axles have always tied into the same general location as the skid plate in the IRO kit.
Without knowing the mounting specifics of the kit and actual upper and lower link separation, itll be hard to say, and since we're talking jeeps and not race cars or lowriders.....
Questioning the joints, or lack of jam nuts, I understand. I'm not exactly sure what joints they use, but have read somewhere that you can upgrade to JJ. Perhaps that upgrade would allow the use of jam nuts?..
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