When in stalling a tower bar (strut bar) that has adjustable preload, it is always recommended to raise the car when adjusting the preload so that the load of the shock upper mounts on the shock towers is relieved and balanced. When raised and the the tower bar placed on the car, the preload can be adjusted and set. After it is bolted on and the car lowered back to the ground, each shock tower will have equal load and will prevent independent movement of each shock. Of course you don’t need to have the car completely off the ground just enough get the weight of the car off the shock towers.
This will provide a noticeable difference after installing as opposed to negligible benefits if the bar is not preloaded. Tanabe Sustec Tower Bars are one of the few brands on the market that offer a preload adjustable tower bar. For more info, please check the Tanabe website.
And now here are some random pictures of Tanabe Tower bars installed 🙂