If you run a front swaybar, ES bushings for the bar and the end links help with response without adding more stiffness.
The rear panhard bar and poly trailing arm bushings don't add much, if any, NVH. At least, not compared to poly engine mounts. I still have one nagging rattle on the right rear when the car goes over bumps. Must wait now until it comes back from the body shop.
When I replaced my rear AGX's, I looked closely at my Hyperco's. They showed no signs of spring binding (coils compressed on each other). That means the spring rate will be progressively stiffer throughout all the normal suspension travel on our cars.
The spring design formula is: Force (or weight ) = k (spring constant) * X (deflection). With progressive springs, k is not a constant. It increases with force (cornering weight transfer) and/or deflection (bumps).
The rear panhard bar and poly trailing arm bushings don't add much, if any, NVH. At least, not compared to poly engine mounts. I still have one nagging rattle on the right rear when the car goes over bumps. Must wait now until it comes back from the body shop.
When I replaced my rear AGX's, I looked closely at my Hyperco's. They showed no signs of spring binding (coils compressed on each other). That means the spring rate will be progressively stiffer throughout all the normal suspension travel on our cars.
The spring design formula is: Force (or weight ) = k (spring constant) * X (deflection). With progressive springs, k is not a constant. It increases with force (cornering weight transfer) and/or deflection (bumps).