They are not really squishing or compressing...They are more preloading. The shocks and springs are made to absorb pot holes and such.....when these cars wheel hop it is VIOLENT! The subframe bounces up and down like crazy. when you preload the bushings it lets the car smoothly transfer the power instead of violently. The less violent nature is going to be easier on everything in the rear suspension in my opinion , including the bushing. Think of a person being pulled on an innertube behind a boat in choppy water....If the person lies loosely on the tube the person bounces wildly out of control....the person hits hard in pain and gets thrown off......Now take that same person and strap him to the tube or have him hold on really tight.....he now moves more fluidly with more control and can easily stay on with much less pain because it is much less violent.