Rubicon Owners Forum banner

Flex joints - pros and cons of what's out there

4K views 22 replies 15 participants last post by  SavageSun  
#1 ·
We have available OEM rubber bushings, poly bushings, RE superflex joints, RK Krawler joints, Currie Johnny Joints, Skyjacker Heim joints, etc. How about a discussion of how each of these designs are working out? Not a mine is better than yours slugfest, but more information than the vendors make available. I have read that some joints are maintenance free, while others require constant maintenance and/or replacement. All claim great flexibility. Your observations and experiences please.
 
#3 ·
As someone in the planning stages for a suspension lift, I too would be interested in hearing from the owner/users of kit with these components. From what I can see, most of the "flex joints" are fairly similar in design, pretty durable and can be easily rebuilt in a home garage. Don't the heim joints Skyjacker uses require a hydraulic press to rebuild them? C'mon, let's here from you guys and gals that have been running these joints for a while.
 
#5 ·
I can only truly comment on the RE's, but I do know of two others. I have their superflex joint and other than adding grease to it, I did nothing and it was still tight and in great shape after 30K+ miles of use. It gave great flex and I will probably buy RE stuff again, if not JKS or Currie.

RK had a serious problem with exploding joints about a year ago. Since then they have changed ownership and are trying to make right what was so wrong with them. From what people have posted, most think that their system was right for their needs, but a few have problems with the joints developing lots of play in them real fast.

I have yet to read a complaint about Currie JJ's. Most fabricators that make their own long arms bought Currie's JJ b/c they are tough and available with a bolt welded to them making adjustable arms easy to fab. I *believe* Clayton uses Johnny Joints from Currie in his systems. But last time I saw his post was months ago when he sold his ZJ buggy.

Well, that's what I know, take it for what it's worth.
 
#6 ·
This post I made a week or so ago got a few responses to a similar question. Granted, I was wondering what was basically the lowest maintance and most indestructable for the mud, but it has a little bit of information you may find useful.
http://www.rubiconownersforum.com/phpbb ... hp?t=10278

Based on my intreptation of the responses, I am thinking that rubber bushing joints require the least maintance given their lack of moving parts, so that's the way I think I am going to go due to the abrasive nature of my particular area and the fact that flex isn't really a big concern of mine as long as I don't somehow make it worse than stock. :D
 
#7 ·
From my personal experience wiht RE joints, they work well but just make sure you anti-seize them or get greaseable bolts. We have dealt with more than one jeep having the bolts actually seize to the joint which is a royal PIA to deal with when you are working on the suspension. I have the Rock Krawler suspension now and the actual krawler joints are fine, their rubber bushings suck and have already pushed out after about 1000 miles. I am just going to replace them with the crawler joints. They are at least rebuildable so if they start getting noisy I can just slap a new race in them. The johnny joints seem very similar to the superflex joints with the exception that they get grease from the inside instead of the outside, This will cure all of the troubles that I had with my superflex joints so maybe they will hold up better?? We shall see with elff's clayton kit.
 
#8 ·
another question that i've been pondering myself lately. I'm not a hardcore off-roader so max flex is not of prime concern to me. Durability and ease of service is more important. It seems from what i've read on this subject so far that the stock rubber bushings have some advantages for my needs: basically service free, last a long time, good sound and vibration damping. But it seems that most lift makers cater more to the "max flex is every thing" crowd. I think the ideal set-up for me would be a system that uses upper and lower, front and rear adjustable arms with stock bushings. I've looked at a couple of companies arms that use stock rubber bushings but they are either too pricey, for what they are, or they have something else I don't like. I've been thinking about the RE 4.5" SF with 3.5" springs. Just wish it was available with all rubber bushings in place of the flex joint.

On the joints, does greasing them require disassembly or do they use a grease fitting? If it just takes a squirt from my grease gun on occasion that's not a big deal as far as the maintanance issue goes but since this is for a DD I still wonder about the vibration and noise transmission issues.
 
#10 ·
I think the ideal set-up for me would be a system that uses upper and lower, front and rear adjustable arms with stock bushings. I've looked at a couple of companies arms that use stock rubber bushings but they are either too pricey, for what they are, or they have something else I don't like. I've been thinking about the RE 4.5" SF with 3.5" springs. Just wish it was available with all rubber bushings in place of the flex joint.
check out the nth* upper adjustable arms. im using them and love em.
if i were looking at a lift that is basically verry low maintenence i would consider jks lower arms (bomb proof) and nth* uppers (strong enough for uppers and cheap)
anyway just my opinion.
 
#11 ·
James said:
Never seen an un-happy user of JKS arms

What I plan to use w/ RK 3-link uppers
Yeah, they do look to be what I'm looking for but, see my above comment about "too pricey". MSRP on them according to their site is $340 a pair for the F/R lowers, $300 a pair for the Front uppers and $280 a pair for the Rear uppers. Lets see, that comes to $1260 just for the CAs. The whole RE 4.5"SF kit with 3.5" springs can be had for less. By the time i built a full kit using all JKS arms, TB, disco's, RE 3.5" springs and all the other assorted bits I would need it would probably be more than the RE LA kit.
 
#12 ·
I personally think the johnny joints are the best. Lube from within unlike RE/RK, the joint is poly so it does have some give to it, unlike heim joints etc.... I have not heard of anyone having problems with them. Most people will say they don't like them because you can only adjust the preload with different width shims and it takes a press to put them together with any ease, but once they are put together right they last a really long time and you could always carry a spare on the trail so you don't have to mess with trying to put one back together with out a press.

The stock rubber bushing is excellent also.

Nth degree says they are coming out with a completely new joint design. Should be interesting.
 
#13 ·
Imaposer said:
James said:
Never seen an un-happy user of JKS arms

What I plan to use w/ RK 3-link uppers
Yeah, they do look to be what I'm looking for but, see my above comment about "too pricey". MSRP on them according to their site is $340 a pair for the F/R lowers, $300 a pair for the Front uppers and $280 a pair for the Rear uppers. Lets see, that comes to $1260 just for the CAs. The whole RE 4.5"SF kit with 3.5" springs can be had for less. By the time i built a full kit using all JKS arms, TB, disco's, RE 3.5" springs and all the other assorted bits I would need it would probably be more than the RE LA kit.
I run all JKS lowers and front uppers, combine their price (not msrp) from Mike at the rockshop and the RK rear setup I have and I am close to the RE SF 4.5 but with a better setup in my opinion. The JKS arms are much beefier, and the RK setup in the rear let me ditch the trackbar. I am very happy with my setup.
 
#14 ·
flex joints - pros and cons of what's out there

Mudzilla, thanks for the reference to your previous thread. Your subject definitely ties in with this one. Referencing Imaposer's desire for RE adjustable arms with only rubber bushings, they do exist, but only for the lowers, #RE3720 @$200/pr. I think this discussion is going in the right direction, just hoping more people weigh in with their personal experience.

I recently spoke with a Currie rep about the history of the johnny joint. Curiosity was getting to me because of the similarities of the Currie and RE joints. He said it was developed by John Currie, but the original design dated to the 1940's, where it was invented by one of the big truck mfgs, so there could be no patent.

I've been reading this forum for six months (plus all the archives) hoping for the information I'm now getting from this thread. I hope it helps each of us to pick the suspension components we need from the wide array of options. Please keep the info coming in!
 
#15 ·
I like the Currie Johnny Joints. For all reasons stated above. For some real flex check out the new Jimmy Joints.

EDIT

Can't find link for the new Jimmy Joints. Poly Performance I believe is manufacturing them, most other joint have around 30 degrees of movement where these have over 70 degrees.
 
#16 ·
One thing that you should look at is that JKS arms do not have "flex" joints. They are simply stock rubber bushings, the whole arm is designed to twist instead of the actual joint. Some will say that this puts more pressure on the axle and frame mounts, but I have seen control arm mounts break off of the axle with both "flex" joints and factory style rubber joints.

You can break the control arms available down into three categories, ones that use flex joints(currie, RE, clayton, etc), ones that use factory style bushings(tera flex, JKS, superlift, etc) and ones that use heims or rebuildable heims(rockkrawler, skyjacker, etc)
 
#17 ·
JKS arms will basically relieve pressure like a stock arm. The bushing distorts and like a stock arm, it will twist around its axis. The JKS will twist more then a stock arm but I wonder how much of a difference it really makes from the perspective of relieving stress on the mount. Since the suspension moves in an arc the only real way to relieve all the pressure on the mount is with a joint that can articulate in all directions (except the axis of compression/tension from end to end) and it also must be able to articulate enough or else it will start to put a lot of pressure on the mount. The JKS arms are great for what they do. They are basically a beefed up, adjustable stock arm that will rotate around its axis even more then a stock arm. In a long arm, I think one stock rubber bushing and one flex joint is the way to go. It probably does put more stress on the mounts then an arm with flex joints on each end, but the rubber will dampen a lot of vibration.




turtle said:
One thing that you should look at is that JKS arms do not have "flex" joints. They are simply stock rubber bushings, the whole arm is designed to twist instead of the actual joint. Some will say that this puts more pressure on the axle and frame mounts, but I have seen control arm mounts break off of the axle with both "flex" joints and factory style rubber joints.

You can break the control arms available down into three categories, ones that use flex joints(currie, RE, clayton, etc), ones that use factory style bushings(tera flex, JKS, superlift, etc) and ones that use heims or rebuildable heims(rockkrawler, skyjacker, etc)
 
#18 ·
OK, I'll admit I'm a Jeep idiot which is why I'm here, trying to become less of an idiot. I don't have my jeep yet so I really can't look at the suspension components to visualize the movements involved. I guess it would help to see a jeep on a ramp so I could see exactly how things were twisting and turning. Just trying to visualize it, it seems to me that an arm that twist would create less stress on the mounts than a similar arm that doesn't. Is there a high incidence of failures among JKS arm users?

I don't plan on becoming a hard core rock crawler. This vehicle is going to be my DD and just a general purpose off-roader. For my style I don't think flex is the big issue. So, is the stock arm bushing design really a problem for that purpose? At what level of off-roading does it become an issue of twisting or ripping off mounts?

I'm just trying to find the best compromise for my intended, real world, use. Like in many other things, we have the tendency to want the best, baddest thing avaiable even though it may be more than we need. I have the natural tendency to do this in most of my pursuits, so I'm trying to temper my buying decisions with a healthy dose of reality based on my real NEEDS.
 
#19 ·
Imaposer said:
Just trying to visualize it, it seems to me that an arm that twist would create less stress on the mounts than a similar arm that doesn't. Is there a high incidence of failures among JKS arm users?

I don't plan on becoming a hard core rock crawler. This vehicle is going to be my DD and just a general purpose off-roader. For my style I don't think flex is the big issue. So, is the stock arm bushing design really a problem for that purpose? At what level of off-roading does it become an issue of twisting or ripping off mounts?

I'm just trying to find the best compromise for my intended, real world, use.
I wouldn't worry about horror stories of jeep failures with certain parts so much. Failures happen because of mistakes, either installing or while driving, and sometimes just because of dumb luck. People lose CA mounts with all kinds of lifts, and I'd venture to say I could probablly get mine torn off of my stock suspension rather easily as well by means of a large rock.
It just the game we all play, almost every modification made opens up a can of worms to another needed. As long as you're gonna play it, you may as well get what suits your needs, rather than your fears. :wink:
 
#20 ·
Most failures of control arm brackets do not occur do to installation mistakes, or even driving mistakes, they happen from increased stress on a part that was not built to hold up to increased tire size and the stress they put on the mounts. I have replaced 6 front LCA mounts(4 of 6 were completely ripped off on the trail), all but one was with 35" tires the failure that occured on the 33" tire was someone who wheels the hell out of his jeep. All but one of the failures occured with stock type bushings and the one was a superflex joint. I have repaired and braced 2 LCA mounts where 31" tires where being run. Oddly enough he had poly bushings in his LCA's. Use that information for what it is worth, I know what I reccommend to my wheeling buddies who go bigger than 33's.
 
#21 ·
If the poly bushing was the same style bushing as a stock bushing but only in poly instead of rubber, then those are the worst you can get. They put so much stress and cause so much bind that it is only a matter of time before a mount breaks off. It is a big problem if both ends of the control arm use it. If one end has something that can flex then it might be OK.

I don't understand why manufactures use them. I think FT stopped using them in there basic 4" lift. Now sometimes they make that bushing with a very stiff center section and two seperate outer sections that are much more compliant. I think rancho does this on their arms.






turtle said:
Most failures of control arm brackets do not occur do to installation mistakes, or even driving mistakes, they happen from increased stress on a part that was not built to hold up to increased tire size and the stress they put on the mounts. I have replaced 6 front LCA mounts(4 of 6 were completely ripped off on the trail), all but one was with 35" tires the failure that occured on the 33" tire was someone who wheels the hell out of his jeep. All but one of the failures occured with stock type bushings and the one was a superflex joint. I have repaired and braced 2 LCA mounts where 31" tires where being run. Oddly enough he had poly bushings in his LCA's. Use that information for what it is worth, I know what I reccommend to my wheeling buddies who go bigger than 33's.
 
#22 ·
James said:
Never seen an un-happy user of JKS arms

What I plan to use w/ RK 3-link uppers
James
Just to clarify

RK no longer makes a 3 Link upper. That was part of their Gen I kits.

It is now a 4 link with 100% separate Left and right upper control arms.

Turtle pretty much covered my comments on the RE Superflex joints.
I have since converted to Currie Johnny Joints but have not had them long enough to provide any durability tests.
They do flex great tho
 
#23 ·
I have run all Teraflex and they were good, gave me good service for about 35k miles and were ready for a rebuild. I switched to JKS and am convinced they are the some of the best engineered and bullet proof ones out there. You can get them on sale if you look around. I like the OEM bushings which are a breeze to replace. They are threaded with 16 threads to the inch which make for very fine adjustments.

http://homepage.mac.com/donpryor/PhotoAlbum7.html