"What the spacers do is pre-load the stock rubber bushings so the body does not float separately from the subframe. Stock, the body floats about an inch before the suspension does anything. Installing the Spacers will cause the Zs body to lean much less.
One of the reasons Zs wheel hop is because the sub frame is mounted loosely causing the subframe to bounce up and down. Pre-loading the stock bushings results in much more responsive handling and also greatly reduces wheel hop. Also by retaining the stock rubber mounts you're still isolating noise and vibration, versus replacing them with solid aluminum or delrin; which can be harsh."
