Bilstein 5160 shocks up front.
It has a .5 inch body lift, 31 inch tires, 3.25 inch backspace wheels, and 7 inch fenders. The tires don't touch anything at full stuff.
Does control arm bushing composition affect ride quality or NVH?
- Thread starter bobthetj03
- Start date
It has a .5 inch body lift, 31 inch tires, 3.25 inch backspace wheels, and 7 inch fenders. The tires don't touch anything at full stuff.
Well, after a long delay over the summer I finally got my Rancho D2 control arms all installed. These are the arms by Rancho with the D2 bushings which are basically the same thing as the Synergy DDB. I did take a NVH reading with my phone app across some railroad tracks this spring with my old arms, but it was so long ago, I don't know if its worth checking again with my new arms. So any semblance of a scientific observation is pretty much out the window. So I guess like every other Yahoo on the forum, all I can do is give you my seat of the pants observation. So here is the process I went through and what I found:
My first order of business was replacing the front upper axle bushings. I had a local shop press out the old Clevite and press in the Synergy bushings that are made for the JK upper axle. I don't know how much work it was but I know they did crush the pasenger side bracket and had to use some heat to straiten it out. I also noticed the bushing now fits slightly loose in the bracket. I was able to jiggile it in and out by hand. I had to be very methodical about it. But I did get it out and back in by hand. I expect that it won't take long for rust to form around it and it will be rusted into place. But it does cause concern and like others I may need to find some adhesive or something to hold it into place better. In hind sight I would maybe purchase the Currie front axle kit and forgo the DDB bushing in this location. Anyway, onto the review of the arms and bushings.
After installing the DDB in the front upper axle mounts I thought I could feel a small of improvement. Maybe placebo effect or confirmation bias. I'm not sure, but it seemed a little better.
I installed the rear arms a few months ago. Again things felt better. A little more planted and less movement in the rear. Again, placebo effect or was it real. Its hard to say.
Finally, after dealing with other house repair projects that took priority over the summer, last weekend I finally got the front control arms installed to complete the whole set of 8 arms. Again I felt improvement. This time it was more pronounced though. The steering on the Jeep feels tighter and the whole jeep feels more solid and planted to the road more firmly. It feels more controlled and less prone to wander. I was expecting this though. So is it confirmation bias or did it really tighten up my steering?
What I wasn't expecting though, was a reduction in harshness through the steering wheel. In the past, driving over rough surfaces always transmitted very abruptly through the steering wheel with an impact and a shudder. Any bump seemed to really shake the wheel. Not bump steer or death wobble or anything like that. It just really felt harsh and loose. The best term I can think of is that the steering wheel just shuddered in my hand. That is gone now. It took me by surprise. I wasn't expecting this. So I still need to drive over some rough potholes and roads for further confirmation. But is seems that the shuddering that I had in the steering is gone. When I hit a pothole or rough patch now, I feel the immediate impact and that's it. Just one impact, not the loose shuddering sensation that I felt before.
So overall, I am very happy with the Rancho D2 control arms. i think they have greatly improved the comfort and control of the Jeep. Now, to be clear, my Jeep had the stock control arms with 110,000 miles on them. Some of the bushings looked really good but a couple were starting to pull away a little. Most were weather checked and cracked. So certainly after 14 years and 110,000 the stock bushings were not performing at optimum levels. I might have gained the same benefits by simply replacing my arms with Moog factory replacements for $200+/-. I also can not speak to how a Currie JJ would have made the Jeep feel.
As far as actual Noise, Vibration, and Harshness. Well, I never had noise and vibration before. So there was nothing to correct. However, as I mentioned above, the harshness/shudder through the steering wheel has been improved. A passenger in the Jeep may not notice the change. But as the driver, there is a noticeable improvement in control and smoothness of response.
My first order of business was replacing the front upper axle bushings. I had a local shop press out the old Clevite and press in the Synergy bushings that are made for the JK upper axle. I don't know how much work it was but I know they did crush the pasenger side bracket and had to use some heat to straiten it out. I also noticed the bushing now fits slightly loose in the bracket. I was able to jiggile it in and out by hand. I had to be very methodical about it. But I did get it out and back in by hand. I expect that it won't take long for rust to form around it and it will be rusted into place. But it does cause concern and like others I may need to find some adhesive or something to hold it into place better. In hind sight I would maybe purchase the Currie front axle kit and forgo the DDB bushing in this location. Anyway, onto the review of the arms and bushings.
After installing the DDB in the front upper axle mounts I thought I could feel a small of improvement. Maybe placebo effect or confirmation bias. I'm not sure, but it seemed a little better.
I installed the rear arms a few months ago. Again things felt better. A little more planted and less movement in the rear. Again, placebo effect or was it real. Its hard to say.
Finally, after dealing with other house repair projects that took priority over the summer, last weekend I finally got the front control arms installed to complete the whole set of 8 arms. Again I felt improvement. This time it was more pronounced though. The steering on the Jeep feels tighter and the whole jeep feels more solid and planted to the road more firmly. It feels more controlled and less prone to wander. I was expecting this though. So is it confirmation bias or did it really tighten up my steering?
What I wasn't expecting though, was a reduction in harshness through the steering wheel. In the past, driving over rough surfaces always transmitted very abruptly through the steering wheel with an impact and a shudder. Any bump seemed to really shake the wheel. Not bump steer or death wobble or anything like that. It just really felt harsh and loose. The best term I can think of is that the steering wheel just shuddered in my hand. That is gone now. It took me by surprise. I wasn't expecting this. So I still need to drive over some rough potholes and roads for further confirmation. But is seems that the shuddering that I had in the steering is gone. When I hit a pothole or rough patch now, I feel the immediate impact and that's it. Just one impact, not the loose shuddering sensation that I felt before.
So overall, I am very happy with the Rancho D2 control arms. i think they have greatly improved the comfort and control of the Jeep. Now, to be clear, my Jeep had the stock control arms with 110,000 miles on them. Some of the bushings looked really good but a couple were starting to pull away a little. Most were weather checked and cracked. So certainly after 14 years and 110,000 the stock bushings were not performing at optimum levels. I might have gained the same benefits by simply replacing my arms with Moog factory replacements for $200+/-. I also can not speak to how a Currie JJ would have made the Jeep feel.
As far as actual Noise, Vibration, and Harshness. Well, I never had noise and vibration before. So there was nothing to correct. However, as I mentioned above, the harshness/shudder through the steering wheel has been improved. A passenger in the Jeep may not notice the change. But as the driver, there is a noticeable improvement in control and smoothness of response.
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Interesting observations. I remember after installing the JJs, I had similar thoughts. That the Jeep felt tighter, more responsive and just nicer.
I had read that in the forums years ago about JJ and always wanted to install JJ just to improve the handling and response. But I didn't think it was worth the money just for the ride and handling improvement. Now that I have the D2 arms I realize what I've been missing out on. I need to get out and drive more this fall before winter comes to really enjoy them. My LJ is at the point where I like to store it over the winter and avoid the salt roads.
This is might be an anecdotal comparison, but it feels relevant to this. Earlier this year, I switched from a soft polyurethane JKS body lift to a rigid aluminum Savvy body lift. Along with all the other improvements, something I immediately noticed was how quiet the cabin was now that the body/frame connection was actually tight and relying again on the factory isolaters for the first time in 6 years.
I still believe that a tight snug connection is a quiet connection.
OP
I felt similar effects when I had Currie arms up front, and then again when I switched to MC arms.
I'm having a hard time seeing how a poly body lift vs a aluminum body lift makes a difference if they both have the factory rubber isolator on top... Oh wait. Did the JKS replace the rubber isolator? That would do it
I agree with the snug connection statement. I think JJ or even new Clevite could have achieved a similar result. But maybe not the same. Would Clevite be softer and maybe continue to allow some shudder, would JJ be firmer and allow more NVH? That I don't know. Do the DOM tube arms have any affect on the control and stability of the Jeep versus the flexy U-channel factory arms? I don't know that either.
I do know that when I used a large punch in the mounting bolt hole of the stock arm and twisted it, the stock arm would flex before the Clevite bushing would flex. I was amazed at how easily the stock arms flexed. The bushing barely crushed but the arm flexed like mad. I thought I would bend and crush the arm by hand. And I'm not very strong.
So I wonder how that flexible U-channel arm affects the feel of the Jeep. The impact of a pot hole or something is obviously on a different axis than the direction of flex. So maybe it has no impact, but the ease at which it flexes was something and it seems like it would have some effect. But yet logically, I don't see it.
I will note that with the solid arms and the D2 bushings, my LJ almost begins to feel a little more like my friends old JKUR. His JK always felt more taught and controlled where my LJ always felt loose and floppy . I don't feel that so much now. Now it feels more like the shocks are able to control body motion and i have less flop. But more miles are needed to confirm all of this. That is just initial impressions.
See here. Directly or indirectly, I think it relates well with what is being discussed here.
https://wranglertjforum.com/threads/jks-1-25-body-lift-the-good-the-bad-and-the-ugly.27626/
https://wranglertjforum.com/threads/jks-1-25-body-lift-the-good-the-bad-and-the-ugly.27626/
Here's a new data point for an old thread.
To make a long story short, I had some barely noticeable driveline vibes remaining after a lift and t-case drop. Then when I swapped the rear Moog control arms with Clevite bushings for Savvy control arms with Johnny Joints at stock length (i.e. no change except control arm composition), the driveline vibes were immediately much louder.
My guess is that the rubber Clevite bushings did a better job of isolating the driveline vibration than the poly bushings in the Johnny Joints.
I ended up fixing the vibes with a MML and taking out some of the t-case drop.
To make a long story short, I had some barely noticeable driveline vibes remaining after a lift and t-case drop. Then when I swapped the rear Moog control arms with Clevite bushings for Savvy control arms with Johnny Joints at stock length (i.e. no change except control arm composition), the driveline vibes were immediately much louder.
My guess is that the rubber Clevite bushings did a better job of isolating the driveline vibration than the poly bushings in the Johnny Joints.
I ended up fixing the vibes with a MML and taking out some of the t-case drop.
It took me a little while to follow your logic. I always thought driveline vibes were transfered through the transfer case mounts, but it makes sense that the vibes would also follow the driveshaft into the axle. Which, of course, would transmit the vibes through the control arms. So a softer Clevite bushing could absorb those vibes better. If thats the case it would stand to reason that the Clevite bushings are also absorbing road imperfections better.
In my personal experience with DDB bushings, I did not notice any increase in NVH over Clevite, but there was a definite improvement in control and response of the DDB.
In my personal experience with DDB bushings, I did not notice any increase in NVH over Clevite, but there was a definite improvement in control and response of the DDB.
He is right about making single changes only as a means of determining if it is making a difference. As an avid handloader/shooter/accuracy buff, only change one variable at a time when working up a load. The same logic applies here.
It's not necessarily the case that the Clevite bushings would absorb road vibrations better. The driveshaft vibrational motion may well be along the long axis of the driveshaft, which is nearly parallel to the long axis of the control arms. The Johnny Joint bushings are non-compliant in that direction. On the other hand, road vibrations come in along an axis where the Johnny Joints can rotate, so they can absorb more of that motion.
It does seem like there is a noticeable improvement in small bump compliance with the Johnny Joints over the Clevite bushings.
Blaine pretty much knows his shit. When he gives an explanation it is based on very sound principles and experience.
Doesn't the JJ spin 360 degrees making it compliant in all directions?
Also wouldn't the drive shaft vibrations be horizontal as well as vertical? OR more accurately in all directions around the shaft?
So if you removed the tracbar, wouldn't you be able to move the JJ axle side to side quite a bit? If so, then the JJ is compliant on a vertical axis as well as the horizontal axis and all 360 degress in between. So I don't think I would say the JJ is non compliant in any direction the driveshaft vibes are exherting.
The JJ arm would be non compliant down the length of the arm. But then I think the discussion changes from material composition to control arm angles.
That was the point.
If the vibration from the driveshaft was along that axis, the JJ would transmit it more than a Clevite bushing would. Other than indirect observation, I don't have any evidence that the vibration from the driveshaft was in that direction, so there's certainly some speculation there.
Seems to me the driveshaft vibration would be around the rotating mass of the driveshaft. Making the driveshaft want to move up and down like a tire that is out of balance. But since the vibes are from the joint binding and not a balance issue, you might be correct as to the direction the vibes are coming from.
I can confirm, control arm bushings do not affect ride quality or NVH.
I am in a unique situation. I own and operate a small tour/rental business and have three JL rubicons.
2018, 2019, and 2020.
All 3 have the 3.6, 2" RC spacer lift, factory wheels and tires. All specced from the factory identically (two of them have a tow package, but that's irrelevant). So I have 3 identical jeeps.
At around 15k miles the '18 JLUR had a frame side front upper control arm bushing give up. Keep in mind my jeeps spend a huge amount of time off-road in very rocky terrain. I would put them in the "extreme use" category. Since I knew bushing failure was going to be an issue I chose to replace the entire control arm set, plus front and rear track bars with MetalCloak components. The MC stuff tightened up everything nicely ( fixing the very slight feedback in the steering wheel and pedals others had mentioned) but didn't change anything else (okay, steering is much improved, but that's a JL issue). I doubt anyone could tell they were driving the MC equipped JL vs a factory control arm JL. I drive all 3 jeeps on a daily basis and cannot tell them appart. I'm expecting that when the jeep is replaced from age, I can take the MC stuff off and put it on the replacement. I will post my results a few years down the road good or bad.
I am in a unique situation. I own and operate a small tour/rental business and have three JL rubicons.
2018, 2019, and 2020.
All 3 have the 3.6, 2" RC spacer lift, factory wheels and tires. All specced from the factory identically (two of them have a tow package, but that's irrelevant). So I have 3 identical jeeps.
At around 15k miles the '18 JLUR had a frame side front upper control arm bushing give up. Keep in mind my jeeps spend a huge amount of time off-road in very rocky terrain. I would put them in the "extreme use" category. Since I knew bushing failure was going to be an issue I chose to replace the entire control arm set, plus front and rear track bars with MetalCloak components. The MC stuff tightened up everything nicely ( fixing the very slight feedback in the steering wheel and pedals others had mentioned) but didn't change anything else (okay, steering is much improved, but that's a JL issue). I doubt anyone could tell they were driving the MC equipped JL vs a factory control arm JL. I drive all 3 jeeps on a daily basis and cannot tell them appart. I'm expecting that when the jeep is replaced from age, I can take the MC stuff off and put it on the replacement. I will post my results a few years down the road good or bad.
Thanks kmas0n. That is good info. Kind of... The argument about control arm NVH is pretty much limited to Johnny Joints. I think everyone agrees that other bushing type arms like the Metal Cloak and Synergy DDB arms offer the same NVH as stock Clevite. Its the Johnny Joints that people argue will introduce more NVH.