Rubber vs polyurethane bushings

[Goatman]

I wholeheartedly agree with the superiority of the JJ. No question about it. I think JJVW has explained the differences quite well.
I just don't get how the poly bushings could produce a "harsher" ride. I'm talking when new. Not 10 years old. The poly has to allow the control arm better cushioning than the JJ. I might just be too anal about this question. It's just that it seems these magazines collectively decide on the superiority of something and go in lock step whether they realize they are right or wrong.
Like the Low Center of Gravity thing. They get 1" of up-travel out of their fancy way of setting the suspension up and swear by it to this day, when they HAVE to know that sacrificing all that axle movement is terrible, even on the street. A speed bump will send the truck banging around with no control. Hell, a good corner at any speed will cause the suspension to lock up!
But the poly bushings seem to me to have to be softer than a JJ. And I can't seem to find out why this is argued to be wrong without a valid reason.
I was firmly against a body lift. Then after a good explanation from a few guys here I totally disagree with my former stance. I guess I'm just wanting someone to give an explanation of why they think a poly bush would produce a harsh ride when rubber and steel don't. The durometer of poly is far softer than steel.

 

[jjvw]

Magazines need to sell magazines and people like to be a part of a trend. It is comforting.

In the big thread about control arms and ride quality, I have wanted multiple times to be able to compare rod ends to a bonded rubber bushing on the same vehicle. If there is a difference, I'm not sure it is as dramatic as many want it to be.

 

[freedom_in_4low]

The poly has to allow the control arm better cushioning than the JJ. I might just be too anal about this question...
But the poly bushings seem to me to have to be softer than a JJ. And I can't seem to find out why this is argued to be wrong without a valid reason...I guess I'm just wanting someone to give an explanation of why they think a poly bush would produce a harsh ride when rubber and steel don't. The durometer of poly is far softer than steel.

It seems like you're thinking the JJ is effectively steel on steel like a heim joint but's not. It's a steel sphere in a poly bushing so that it allows misalignment between the axes of the inner and outer sleeves, unlike the steel cylinder in a traditional split poly bushing. So if anything, the harshness between the two should be very similar, if not the same (assuming the durometer of the poly is comparable between the two and the radius from inner sleeve or sphere to housing is similar, which I don't know). The exception might be when the poly bushings are binding up due to the aforementioned misalignment.

Most of this is spitballing compared to some of the more experienced guys here, but what I have experienced is my TJ with poly bushings at both ends of my lower control arms. I didn't notice it being particularly harsh, and I didn't notice a different in harshness when I ditched them in favor of arms with rubber in one end and a mediocre JJ copy at the other. What I did notice was better flex and less creaking during that flex.

 

[BuildBreakRepeat]

I wholeheartedly agree with the superiority of the JJ. No question about it. I think JJVW has explained the differences quite well.
I just don't get how the poly bushings could produce a "harsher" ride. I'm talking when new. Not 10 years old. The poly has to allow the control arm better cushioning than the JJ. I might just be too anal about this question. It's just that it seems these magazines collectively decide on the superiority of something and go in lock step whether they realize they are right or wrong.
Like the Low Center of Gravity thing. They get 1" of up-travel out of their fancy way of setting the suspension up and swear by it to this day, when they HAVE to know that sacrificing all that axle movement is terrible, even on the street. A speed bump will send the truck banging around with no control. Hell, a good corner at any speed will cause the suspension to lock up!
But the poly bushings seem to me to have to be softer than a JJ. And I can't seem to find out why this is argued to be wrong without a valid reason.
I was firmly against a body lift. Then after a good explanation from a few guys here I totally disagree with my former stance. I guess I'm just wanting someone to give an explanation of why they think a poly bush would produce a harsh ride when rubber and steel don't. The durometer of poly is far softer than steel.

Because poly doesn’t flex well - the JJ is a flexible joint rotating in poly. Not relying on the flexibility of poly to move just isolated by it. Look at this comparison of the joints.

 

[jjvw]

because poly doesn’t flex - the JJ is a flexible joint cushioned in poly. Not relying on the flexibility of ploy to move just cushioned by it - more of an isolation.

Which is a key to understanding why that design works as well as it does. The individual components of the joint aren't being asked to perform a task they aren't qualified to do.

 

[BuildBreakRepeat]

Which is a key to understanding why that design works as well as it does. The individual components of the joint aren't being asked to perform a task they aren't qualified to do.

And that sir is the concept your and my builds are modeled after. Not asking components to perform tasks they can’t or won’t made to do, and at the same time optimizing they ability of those componets to their maximum ability.

 

[Goatman]

Because poly doesn’t flex well - the JJ is a flexible joint rotating in poly. Not relying on the flexibility of poly to move just isolated by it. Look at this comparison of the joints.View attachment 120990View attachment 120991

Ok. Now we are getting somewhere.
I was hoping Chris, Mrbills, and others with a lot of west coast type of knowledge would jump in, but I think that you might have finally helped me see the reason. Thanks!