I would say you would find all of your questions answered on the ClubLexus LS430 forums in the sticky's/FAQ's at the top of the page.
if you can't find it, the members there are online more often, an can get your questions answered sooner. . .
I had the Prmacy's on my LS430 until i sold it, but didn't realize how much better the snow traction was until i got my LS460 which has the Michelin Pilot HX MXM4's