...BTW your Bieber avatar is awesome.-Malone
On the left in the pic you can see most of the problem. The stock insert looks like this...the control arm has a radius in the front but not in the rear. It looks like a horn in the control arm see above. The stock front bushing has the rubber to fill the space and is softer. The poly has no radius, it is just empty space. The empty space allows the control arm to rock and slam back and forth...with leverage from the rear part of the control arm being in poly holding that end solid. I worked with my buddy Troy on this as he was having similar issues. If you take a copper tube the same size as the inner part of the control arm and weld that void shut, then ream it to fit and face it off so it is exactly the same length as it was with the radius life is good. Troy has a 12.8 second 1/4 mile rabbit...it is a 1.8 8v with a cross flow head, turbo, and most days nitrous. He goes through 2-3 020 transmissions per year drag racing, it is not a calm ride or trailer queen. He drives it at least 5,000 miles in the summer. Since we did this mod a couple years ago he hasn't had a control arm failure, used to go through them at least once per season. To make it worse on the control arm we seam welded it at the same time, so all the vibration and torque is multiplied in the stiffness of the welds and the poly mounts.I think you are right Chris, but it is because the poly is not the correct shape for the arm, not just because it is hard.