Reducing bushing compliance in certain directions allows the suspension components to move only in the directions in which they were intended, and respond more accurately. This gives your car sharper handling, better feedback, and generally more stability when cornering or braking. Additionally, the car can feel quite sloppy if the factory rubber bushings are worn and soft or even torn, and replacing them with anything intact will provide a noticeable improvement.



Be aware, polyurethane bushings can cause suspension components to bind up. As bushings are designed to allow free movement in a certain direction, stiffening them enough to reduce compliance in all other directions may prevent it from moving freely in the direction it was designed to. However, this is not an issue with most of the upgraded bushings in our cars, as long as the center sleeve is re-used and you properly lubricate the bushings. Oh, and try to torque the suspension bolts with the wheels on the ground if at all possible. You can also use a jack under the ball joint for each wheel while you tighten the bolts for that corner.



The other issue is of course increased NVH. By reducing compliance, they will transmit more felt vibrations and impacts to the car, and generally noise as well. However, this will not be very pronounced if you only replace the control arm bushings and trailing arm bushings. As I indicated to Kane, and he to you, replacing the shock mounts and spring seats with poly is where you really get into some NVH issues, and the benefit of poly here is not nearly as pronounced as with other bushings. If this is a street car, I HIGHLY recommend you replace shock mounts and spring seats with new KYB rubber. The control arm and trailing arm bushings won't be so much of an issue, as those bushings in rubber didn't really do much for your ride quality in the first place. However, they will make the response a bit sharper, so if you have stiff shocks and springs, they will make them seem a bit harsher. My advice is to lube the bushings properly, use rubber where I instructed, and deal with what mild NVH increases you get, or forget the whole thing. It can be a great upgrade to improve the overall responsiveness of your car for fairly cheap and without too many drawbacks if you do it right.