I don't know how common it is but I ran into some poly bushing that were not coned shaped and thus had no articulation when tightened up at the shackle. It road like a hay rack. The Hotchkis springs on the other hand moved freely on the shackled when tightened. I also had some other springs that I compared and the rubber bushing were coned shaped on the end. The shackled should tighten down to the metal insert in the bushing and be able to move.