I'll put my opinions in this thread to counter the BS posted about polyurethane bushings.....again.

When properly designed and used, poly bushings do not "bind" as claimed. in fact, ALL rubber bushings are ALWAYS in a bind when the suspension is moved. That's why you have to lower a car to ride height before you tighten the bushing fasteners. On rubber bushings the rubber is BONDED to the sleeve and shell. The sleeve CANNOT rotate relative to the outer shell without imparting shear loads (twisting) of the rubber. It's physically impossible.

Poly bushings are designed to rotate on the inner sleeve. That rotation facilitates articulation of the suspension, especially when a proper lubricant is used. There is no twisting of the poly like there is of the rubber. Properly designed poly bushings don't induce friction or constrain movement like rubber bushings do.

On my mockup C4 suspensions used for building shock mounts I have the stock rubber bushings. When the front a-arm shafts are tightened down, it's almost impossible to move the suspension by hand. I have to loosen the large nuts on the shafts to get them to move. Also, when the stock dogbones and strut rods are tightened down, the rear suspension barely moves by hand. When a rubber bushing tears, it squeaks like crazy.

I used poly bushings on both my front and rear C4 suspensions. However, I modified them so they fit the way they're supposed to fit. I measured the width of the dogbone sleeves and I made the bushings just slightly larger so they were lightly compressed (about 0.010") from the sides when the bolts were tightened down. I did the same on the front lower a-arms. After greasing and tightening, the rear suspension moves just like it had heims. The front suspension articulates so well I had to set it on boxes to hold it in position. The poly bushings are NOT rigid, so they absorb some deflection of the parts due to misalignment. There is no "binding" at all, and the displacements in the C4 suspension are small as I pointed out in another thread with this misleading BS posted on it.

The reason rubber is used for OEM applications is because it's cheap, and it's softer so it reduces NVH. Rubber doesn't hold the suspension components in alignment very well, that's primarily why they're replaced for performance applications. Poly is a compromise between harder materials like aluminum or delrin and rubber as far as NVH goes. It gives better control of the suspension components and still absorbs some vibration.

I personally think that using heims on the C4 dogbones for anything other than racing is a BAD idea as they absorb most of the shock from road irregularities and transmit it to the frame. IMO it's the WORST place to use them due to the shock loads and the wear that causes them to rattle over time. The strut rods don't have to absorb those shock loads, they just move up and down but they can still transmit some vibrations.

My experience is that manufacturers can't account for all the variables in some poly bushing applications, so they simply make them larger than required and people crank them down, compressing them too much. That causes a lot of friction and poor articulation of the suspension. The preload on a poly bushing is caused by making the sleeve larger than the hole, so it needs to be pressed in. There doesn't have to be preload from the sides, just a way to constrain the bushing.

If rubber was so good there would be a huge market for it and nobody would buy poly. But poly is known to control suspension deflection better than rubber for performance applications. It's been the material of choice for decades. You can hardly find rubber bushings for many applications, like the C4 and C5 Corvettes. All the aftermarket bushings for them are poly or delrin, or similar.