[kevmurray]

TC I agree that no performance car should use rubber. My post was intentionally brief and in hind sight a bit unclear. I think rubber bushings are good for comfort in a street car. When I said "rigid arms" I literally meant the arms, excluding the bushings. Unboxed factory arms deflected but modern tubular do not. This is why I recommended bushings that either give (rubber) or allow articulation outside of a plane (spherical).

I know of racers who have had success with poly bushings but in my opinion spherical is better in this regard. Heim joints are fine for racing but roto and johnny joints have a little more NVH reduction because of the Delrin. Key word being "little." They also last longer than heims and can be tightened and rebuilt. I have heard of some with a poly isolation layer but who offers them escapes me.

On the cause of bind I respectfully disagree with you. Bind occurs when a suspension member does not track the arc dictated by it's bushing. Bind is what causes a bushing to twist, not the other way around. Any sort of spherical bushing allows its member to travel outside of a plane. Rubber and poly do also, but do so through distortion of the material. Rubber simply is higher compliance and so gives more easily. Poly resists more and so there are much greater resistive forces at play (which eventually evacuate the grease and cause the squeaking, I think we agree on this).

Joe, my intended message was to use rubber if you want a comfortable street car or spherical types if you more precise handling and can tolerate increased NVH. I went all spherical in a street car and don't regret it one bit. To give you more context on my setup I have a GM A-body with one inch drop springs that are firmer than stock but not crazy, Bilstein shocks off the shelf, and rubber body bushings.