The inner sleeve in the DDB isn't bound. I rotates freely and can slip from side to side when unbolted. The bushing also has the same degree of deflection as a standard width JJ. An exception is the narrow JJ, which has 40 degrees of deflection.
It might be a slight press fit with the DDB's, but the Giiro's are falling out...
Keep us informed. I ordered the Rancho arms with the similar D2 bushings. I really wanted Synergy, but the lower arms were discontinued before I placed my order. I then lost confidence in them when I realized they were no longer supporting the TJ platform. If some big company could purchase the Nth Degree and Synergy product line for the TJ, they would have a nice lineup of top notch products.
My plan for the upper front axle bushing was to get the Synergy JK bushings and just drill out the holes in my control arm to fit the bushing. When I spoke with a Syndergy Tech in the past he said the bushings were the same except the JK used a bigger bolt. I'll be interested to hear what your results are.
I used the JK bushings, just bore out the holes, go to a junk yard, get a set of 4x4 dodge truck UCA bolts, install them and drive it.
I don't recall what he says about rod ends/heim joints, but most of the common control arm joints/bushings have an isolation material as part of their design.
Similar to the differences between spring rates, the assertion is that the differences between joints/bushings are not perceivable. I'll concede just a tiny bit and suggest that the differences are minor to the point of insignificance.
Something else he often brings up is that unless you are only making single changes, how do you know what is contributing to whatever change your are perceiving.
The one thing that people are not doing is actually putting on any true measurement devices and changing any components to due a real experiment. It is still all supposition until real data is provided.
Case in point: I have an aircraft propeller vibration analyzer that dynamically measures the vibrations of the propeller as the engine is running. I installed a propeller on an airplane, ran the engine, and notice a little vibration (not any more than other airplanes). I installed the analyzer, ran the engine and came up with an reading of very rough. I wound up reinstalling the prop 180 degress from where it initially installed, it cut the vibrations in half. During this whole process, I was not able to actually feel any difference in the seat of my pants. The analyzer did notice the difference and provided a real measurement for me to get the vibrations to "good Levels".
I will still fall back that there is no one supplying data with any scientific measurements. While it is relative, someone likes a 240# spring rate vs someone else likes a 180#, just like someone likes johnny joints vs DDB's, but not one person has actually done any vibration analysis comparing different joints. I looked at buying a transducer, but I don't have access or the money to buy a bunch of arms with different joints and conduct the analysis. I think it is worthy cause, just not one that I can afford.There are SO many other factors to consider when you start talking about "ride" in an automobile...I don't think hard, fast data on any one, specific thing will give you any real clue. Each component up to and including your butt has a stiffness and damper in it. Even if we make the incorrect assumption that the stuff that doesn't move (like the frame or the tub) are perfectly stiff and rigid, there are numerous areas that will add compliance along the path to seat of the pants feel. The tires are flexible and contribute to feel. So do the body mounts and the seats. All those items have a stiffness to them, just like a spring.
All of those things combine to create "feel." You can calculate that resolved spring rate (Jeep can, and does). BUT, its not a nice linear equation to say if I increase or decrease this variable the ride will get "better." Better is dependent on who's butt is in the seat. You may also run into areas where resonance happens (all systems can resonate).
So, this, like the spring thread, is all an academic exercise. People might say they fixed this or that...but that doesn't mean that doing the same thing to your jeep will replicate their result. Every jeep is different, and will react differently to any given modification.