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Imped 02-21-2013 12:04 PM

How the Metalcloak Duroflex bushing stacks up
Let me first preface this review by stating that I’m in no way unhappy with the performance of Currie Johnny Joints. I’ve ran them for years and many thousands of miles now, longer than I ran the stock rubber bushings. The goal of this comparison was to put MetalCloak’s Duroflex joint up against what I believe to be the ‘golden standard’ of control arm ends, the JJ. I’ve had experience with most other joints on the market and the JJ blows them out of the water in terms of durability, simplicity and value.

Before I get started on this review, I think it would be useful to disclose how my preferences have been formed and molded over the years. I started out like any other new Jeep owner, fairly clueless—learning to put the soft top up and down was far more important than what was going on under my Jeep. Before owning the Jeep, I was always interested in cars and tinkering but those two interests were never mixed….in other words, I knew absolutely nothing about suspension. But I met a few guys in the area and decided to try the ‘offroad thing.’ I was hooked after my first visit to Attica and eventually, those random few guys became very good friends of mine and IndyORV formed. Fortunately, as I started wheeling more often, I started to work on my own stuff more often as well. By the time I got around to swapping in my current axles and moving up to 35” tires, I at least knew what control arms did but that’s about it. At that point, suspension geometry and the ‘finer details’ were still unknown to me.

-early 2009: RK 4 link with Currie lowers

-You can see the axle wanting to walk under the vehicle

I remember being very worried about the increase in noise, vibration and harshness (NVH) with Currie arms compared to the stock arms I knew and was comfortable with. Some guy named Blaine told me in a very matter-of-fact tone, “quit worrying about things that don’t exist” or something like that. Once I finally got the Jeep back on the road, it had Currie joints all around, maintained the Clevite bushings in the front housing, and was using Rock Krawler triangulated rear uppers with stock frame mounts. On paper, it was an absolute mess but I didn’t know that….I just blindly thought that no track bar = better. But it felt great on the road compared to what I was used to—much tighter and controlled but still very compliant. After that, I stopped doubting that guy named Blaine.

-The RK and Currie arms

-3/2009: Sittin' pretty on 35's

-Maneuvering 'Wedgie' in Attica

As I wheeled that setup, I really appreciated the smooth and silent operation of the JJ but hated the new-found hopping as I climbed up rock walls. Once I started to dive into suspension geometry, I realized pretty quickly that the RK kit that I spent so much money on was really screwing things up….I would have been much better off keeping the stock axle mounts and running a track bar, as far as geometry is concerned. And I was already dealing with the frame-side poly bushings and axle-side rod ends being worn out so those had to be replaced. I believe this was about the time I started to develop some wobbles up front, despite having these nice, tight Currie JJ’s all around. Once I traced that to the axle housing bushings and removed the arms to inspect, I found sleeves that were nearly separated from the rubber elements….combine that with a few of my stock control arm bushings that showed the same symptoms a year prior, and I really started to understand the limitations of Clevite bushings. Shortly after, I was running JJ’s on all ends and the Jeep drove better than ever.

-Climbing a wall in the quarry....well, more like bouncing up it.

-Suspension getting a bit more proper: Gone with the dog legs and factory frame and axle mounts

-Rear view of a much-improved modified short arm 4 link

Fast forward through a bunch of research, wasted time and money, experience with the industry’s offerings, some wheeling between busted knuckles and 4 letter words, and suspension variations and we’re about caught up. Now it should be somewhat clear why I’m such a “research first” Nazi. I myself wasted thousands of dollars and countless hundreds of hours on parts that would later just be removed and scrapped or sold for cents on the dollar and my preferences reflect that--they have gone from being a puddle of muddy water to a Bushnell scope locked onto a bull’s eye. Due to that, I possess a major fault of being very non-receptive to new parts, especially in this segment. I like what I like, I know how to get it, and I don’t really care for anything else. This comparison is a rare departure from that.

-This replaced the mangled and bent RK truss and allowed me to run 2.5" JJ's all around in the rear

-Sittin' pretty with great clearance

-3 link front with mid-length arms

-Pushing the axle back

-Updated 4 link with mid-length arms

When I first caught wind of MC’s Duroflex bushing, I thought, “great, another failed entry into the world of control arm joints.” There are so many wanna-be joints out there it’s comical and none of them come close to the JJ. But, being familiar with the quality of parts that leaves MC’s facility, I gave them the benefit of the doubt and wanted to get a closer look at these. Naturally, I initially attached the Clevite bushing stigma to the Duroflex bushings since they’re rubber and use a vulcanized, bonded sleeve. My dislike for rubber bushings is, in my opinion, justified since I’ve seen plenty of them get torn up and tore up a few myself in years past. Relating these two bushings was my first mistake and I’ll gladly confess that. These operate in a very different way than your average Clevite bushing. Just watch MC’s video on the Duroflex joint and you’ll see that.

-9 months of work complete

-Box o' bushings

It got to the point that I had to try these simply to satisfy my own curiosity. I have a never-ending appetite for knowledge and that all starts with hands-on experience so unless I could actually try these, I can only make half-*** assumptions as to how they feel and hold up. You can see my first response to these, along with a fantastic discussion, here:

This is a nice recap of the Duroflex bushing:

Shortly after, MC posted a video:

Also, here’s John Currie’s JJ video:

After watching the video, my tone changed and so did my level of interest. That really gave me a great view on how the bushing actually worked that was second only to hands-on experience. Instead of viewing these like I view all of the other joint offerings aside from the JJ, I viewed them as a very viable option.

-Empty Currie barrel

-Duroflex bushing inserted into the Currie housing

Everything you’ve read so far was written before I ever had the Duroflex joints in my hands. When I first opened up the package and picked one up, my first thought was “damn, that’s one heavy chunk of rubber.” They feel very durable and could easily kill someone if used as a projectile. There is some flash (excess rubber) left over from the molding process and grooved machining marks present…neither are particularly pleasing to the eye but I don’t think either will cause an issue at all. In fact, the grooves in the assembly may help to hold grease. After discussing this with Doug @ Metalcloak, they wanted a rougher bearing surface so that the force required to overcome the friction between the barrel and bushing was not too low. So, the machining grooves are a non-issue and are intended.

-Duroflex misalignment

Next, I’ll just give a brief comparison between a stock type bushing, a JJ type bushing, and the Duroflex bushing. In a control arm bushing/joint, you’ve got two items—the sleeve and the absorption element around it. In a standard/OE type control arm bushing, the sleeve and rubber element are bonded together. The rubber element is also bonded to the housing or outer sleeve. The sleeve and bushing material are also the same width, leaving little misalignment capability outside of deflection. In a JJ type joint, the ball sleeve is a lone unit that rides inside interlocked, stationary polyurethane bushing halves. It can rotate in all directions inside the bushing and due to the greater sleeve/bushing width ratio, can achieve high amounts of misalignment. Due to the independent nature of the ball sleeve and bushings, there is no self-centering capability. With the Duroflex joint, the ball sleeve and bushing element are bonded, forming a single assembly. That assembly can rotate inside the end barrel, drastically separating it from the OE type control arm bushing. The sleeve/bushing width ratio is also high, allowing for high misalignment capability. But unlike the JJ type joint, the bonded assembly returns to center. More technical discussion on the properties of different ends can be found here:

-Front end complete

So what kind of changes was I expecting before making the swap? I’ve ran JJ’s for a long time and have been very happy with them. I prefer a tight, ‘sporty’ ride in favor of the mushy, numb stock ride and JJ’s, combined with other items, provide that. On paper, the JJ polyurethane bushings absorb less NVH than the stock Clevite bushings due to their significantly higher durometer rating but in real world application the difference is very small, definitely a tribute to Currie’s diligence in finding the correct blend. This allows essentially no longitudinal deflection, providing a near-direct linkage between the frame and axle, increasing positive traction and suspension response. They provide all of the ‘good’ movement (misalignment) and none of the ‘bad’ movement (deflection). Something else that should also be considered is the preload between the ball sleeve and bushings. It takes a significant amount of force to rotate the ball and in theory, this could contribute to less compliance over road imperfections like pot holes, speed bumps and fire road surfaces than something that requires less force.

-Attica last weekend

Due to the fact that MC’s bushings have much more absorption material and are made of a softer rubber, it only makes sense for them to provide near-stock NVH absorption. One could also infer that the softer rubber will deflect more. Personally, my thoughts were that the reactions from the smaller road imperfections (pot holes, expansion joints, etc) would be reduced by some small amount. Since this is a comparison between two excellent products, all differences must be taken into account, whether they are too close to measure or not. With that said, one could also derive that a small improvement in cornering will be realized due to the self-centering bushings. Lastly, I do like the one-piece, sealed unit. While I’ve had no problems with any of the small grit and grime that can get in between the JJ’s center ball and bushing halves, it can happen. Remember, I ran these for three years with no greasing or maintenance of any kind and until I took them apart I couldn’t have told you they were dry. No noises or other issues. When taken apart, they were dirty and dry as a bone but none of the bushings needed to be replaced. Those are my oldest JJ’s and are still in use on another Jeep in Michigan. But with the Duroflex bushing, I don’t believe anything will be able to get between it and the housing walls. If you live in a wet, salty, gritty environment then this should be taken into consideration.

Real world results
The front swap occurred on 2/8 and I wasn’t able to log many miles before pulling the Jeep back into the garage to set her down for another week of work on other stuff, including the rear bushing swap. But from the miles I logged, I definitely felt a difference, more than I expected. There was no loss in tightness or control but there was a gain in ride quality. It may seem honky, but I mainly based the results on the speed bumps in my neighborhood, with some potholes and train tracks thrown in. With just the front bushings swapped in, the difference between the front and rear suspension when going over the speed bumps was evident—the front just floated right over without any drama and the rear was a bit harsher and ‘bounced’ over, for lack of a better term. The same difference was felt on most road imperfections and train track crossings. I got the rear bushings swapped in late on 2/11 but wasn’t able to take the Jeep for a drive until early 2/16 morning. Conveniently, that also was a day scheduled for the Badlands in Attica, IN. Driving the Jeep over the speed bumps that morning, I can honestly say it was similar from going from 30 psi to 15 psi in my tires.

-Haulin' ***


I expected some differences from these, but not quite as drastic as the differences I’m experiencing. When going over these speed bumps before, I always felt the need to slow down a bit so that I don’t get bucked. Now, I can speed up and float over them. Everywhere else—expansion joints, potholes, train tracks, etc.—on the road, the results are the same: tight, controlled, extremely compliant. Aside from ride quality, one other change was very evident—noise reduction. I’ve got a rear bearing issue going on and that provides a wonderful symphony of sound in the form of your standard high pitch whine. Surprisingly, the noise was cut down by a large amount—enough that my girlfriend noticed without me mentioning it, I could comfortably listen to my radio on the highway without having to crank it, and the biggest indicator to me—I was able to hear my tires. I wasn’t able to take any definitive decibel tests but I can say without hesitation that at any speed above 30mph or so, I was never able to hear my tires over that bearing, wind noise and all other sources of noise and now I am.

Disclaimer: The source of the bearing noise will be fixed very soon.

-What goes up must come down....with a pillow soft landing

Now, before my review on the trail, I’ve got to make this clear—my Jeep was down from 3/12 – 11/12 receiving massive modifications. The last time I wheeled this thing in 3/12, it was a totally different animal than it is now. I’ve got a longer wheelbase, flatter arm angles, more up travel, larger tires, and different rear shock valving than I did back then. So, these bushings could just be another small piece of the pie. But, keep in mind that I have driven the Jeep over two thousand miles on the road from 11/12 – 2/13 with JJ’s so I will assume that the differences on the road will translate to similar differences off of it. In short, I’ve never been able to go so fast through the whoops…..not even close. And I was comfortable doing it and the Jeep felt in total control. The suspension was silent and very smooth and I was able to outdrive the Bilstein shocks, as they were hot to the touch once I stopped. Again, that may not be definitive enough for some but it’s the best I’ve got. Given the knowledge I possess of my Jeep and how it behaves, I can honestly say that the MC bushings made a considerable difference at speed in rough terrain.

-Trying to hit the Savvy skid

So, why would the Duroflex bushings make such a big difference when most would agree that going from stock Clevite bushings to JJ’s makes hardly any difference in perceived NVH? That’s a very good question and one I’ve been pondering over myself. Maybe as we slowly change things in our Jeeps, we lose track of the initial baseline (stock) and due to the slow rate of change, the aggregate sum of those changes isn’t totally felt. Maybe the advantages of the JJ—tighter steering, better constraint and more responsive suspensions feel—overshadow the increase in NVH, making it much less noticeable. Or maybe these actually provide better performance than stock Clevite bushings due to the ability to break away from the barrel. Whatever the answer, I’m not sure. I’d love to take a stock TJ with stock bushings and do this exact comparison—stock, MC, Currie. I think the fact alone that I’m a huge Currie supporter should lend credence and validity to the results I feel and if you doubt any of the claims I’m making, please call Metalcloak and try these for yourself as I did.


This doesn’t mean others won’t experience different results. My Jeep is very spartan—no carpet, no inner fender liners, higher durometer rubber transmission and motor mounts, etc. Simplicity and being lightweight are two key goals of my Jeep so it tends to be a bit louder than a stock, fully carpeted Jeep with soft rubber everywhere. With that said, I think the fact that I realized such significant differences in both ride comfort and interior noise should speak volumes.

I intend to continue to run the Duroflex bushings because I love the way they feel and I’d like to see how they hold up under my Jeep. The long-term durability of these bushings just isn’t known. They haven’t been around long enough to prove how long they’ll last so I’ll do my best to get to that point. Until then, the Currie JJ is undisputedly the most durable joint available. But, I enjoy driving my Jeep back and forth to work, to the trail, out to eat, to the bar, etc. and these simply make it more comfortable and enjoyable to do so.

Obviously, this review will be ongoing. I can take more pictures and will be taking a couple more videos in the near future.

Here's two videos from Saturday @ Attica on Red Trail. All ends are Duroflex.

JJ Deflection test video--as you can see, there is no visible deflection. I'll be doing one with the Duroflex bushings as well.

UPDATE 6/7/13
I've got over 1,000 street miles on these bushings, with more trail miles shortly approaching. I'm still very, very pleased with the results and can say without hesitation that these bushings are one of the best changes I've made. The ride quality is just fantastic.

jbg1980 02-21-2013 12:37 PM

Great review!

Jason 02-21-2013 12:52 PM

Well done Connor. Interested in the longevity as well.

bobthetj03 02-21-2013 12:58 PM

Nice review! Let the real world testing continue! My TJ is mostly stock (2.5" lift, JKS TB and Currie front Lower CA's w/JJ's). I noticed a difference right away when I installed the JJ's just in the front lowers! I am curious myself to feel the difference with the MC joints, so much so that I will be getting MC's front uppers and swap out my JJ's in the front lowers with the Duroflex joints. I hope to contribute to the real world testing of these joints and maybe I can give my perspective to this discussion. Great work Imped! Thanks for taking the time to put up this review.

BamaJeepman21 02-21-2013 01:09 PM

Nice. I really think I'll try the MC joints in the Savvy arms if they're a better DD joint.

scot68 02-21-2013 01:35 PM

Very well done. I have been waiting anxiously for you to begin your review process.

Mud Machine 02-21-2013 01:40 PM

Outstanding write up. Thank you very much for taking the time to keep us informed. Nice to hear from someone that actually has used them both and is willing to give us some honest feedback.

lynn 02-21-2013 01:42 PM

I wish our elected officials could be so open minded and willing to experiment for the sake of improvement. ;)

Excellent write up.
This is a thorough review, free of bias.
I especially appreciate that you've shared your history as well as your knowledge and findings. :thumbsup:

Ripper3494 02-21-2013 01:53 PM

im sold lol

ctorres018 02-21-2013 02:00 PM

Imped- Nice review. From what I've heard yes the duroflex joints are a lot more comfortable, but quick question I'm not sure i saw this in your review, do you notice the flex difference when wheeling? It says on the metal cloak site the joints have 28 degrees better articulation. How do you compare the flex from the JJ to the Duroflex? Is it really noticeable on the trail?

Imped 02-21-2013 02:05 PM


Originally Posted by ctorres018 (Post 15010960)
Imped- Nice review. From what I've heard yes the duroflex joints are a lot more comfortable, but quick question I'm not sure i saw this in your review, do you notice the flex difference when wheeling? It says on the metal cloak site the joints have 28 degrees better articulation. How do you compare the flex from the JJ to the Duroflex? Is it really noticeable on the trail?

With either end, I can max out my shock travel while having tons of remaining potential. That's an absolute non-factor in the JJ vs. Duroflex bushing comparison, assuming they're ran at both ends. I run 11" travel shocks at all corners split 50/50 and that hardly makes either end flinch. View misalignment as a nice byproduct, not necessarily a primary reason to go after something like this. There are advantages to good CA ends past the misalignment capability alone.

Also, that difference isn't on a single joint basis. When viewing it that way, the total misalignment of the Duroflex is 17* from neutral and the JJ is 15*. That will never matter unless you're using a standard bushing on one end for some reason.

Boog 02-21-2013 02:08 PM

So glad to hear good things about the Duroflex joints. I have a whole set of MC control arms waiting to go under my TJ.

hustler905 02-21-2013 03:25 PM

How tough was installation in the Currie JJ ends? Did they have to get preloaded or was it as simple as some washers, the rubber barrel, some more washers and a snap ring?

Also, are these the kits that MC sells as "Currie 2.5 JJ" retrofit kits on their site?

Thanks for playing 20 questions!

sjones26573 02-21-2013 03:27 PM

Well, this pretty much confirms what I thought. Will be getting Duroflex in place of the JJ's I was going to get for my 3 link.

bobthetj03 02-21-2013 03:32 PM

Do you still have JJ's at the front axle end?

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