Can you expand on what makes their joints and track bar better?
The track bar I see differences in but straight control arms with a flex joint is difficult to differentiate any major advantages one over another without someone like yourself who's experienced them pointing it out.
I don't have direct experience with JKS's Control Arms, so I'm basing my opinion on what I see on their site...That being said:
Only one flex joint, where RockJock gives you two. I don't think that having a single flex joint will actually prevent any articulation, but my concern comes in where you start flexing that bushing end to the max often. It can move far enough, but its a lot of pressure on the bonded joint. Eventually it will tear and need replacing. Again, if you're not throwing 12" travel shocks on, its probably fine. The arm is also bent when there is no need for it to be.
Looking at the rebuild kit for the flex joint, it appears to work the same as a Johnny Joint, with one less washer. I don't know how much preload they include on the joint,
but I don't see a compression tool mentioned anywhere
, so maybe not enough. I also don't see any grease channels, or a castellated perimeter like the JJ, so I don't think the zerk would be effective here either, again, unless they don't have enough preload.
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dit: Looking at the rebuild kit install instructions, they require the use of a press tool similar to Rock Jock's. So, maybe they do have enough preload. Would not surprise me if the joint is VERY similar to a johnny joint, since JKS made quite a bit of Rock Jock's stuff when it was Currie. We all know the grease zerks are pretty useless on a Johnny Joint as well, so I don't see any real advantage/disadvantage comparing flex joints themselves.
FWIW, I don't care for Rock Jock's Single adjustable lowers, or anyone's single adjustable lowers. They are a real pain to use when you're trying to dial in pinion angle, caster, axle position, etc. I made mine double adjustable after setting up my suspension once...it was too much for me to bear!
On the track bar, the bends are better positioned on a Rock Jock. Plus, you again get two johnny joints, instead of a pseudo JJ and a rubber bushing. The Rock Jock also uses a forged axle end for adjustment vs the JKS bent steel...and I bent mine twice (which is a big reason I now have Rock Jock). I believe the rear track bar is more advantageously bent too, but that is hearsay, since I've not had any direct experience with that. I do know that I had to move my mounting points around to get my JKS rear bar to clear the Savvy tank skid and rear shock mounting crossmember. Once I did that, its been a non-issue.
Hope that helps.