I have two sets of 18 inch carrera 5-spoke wheels with a set of PS2's on one for summer and Falken 512's all-season for winter. I will second the comments on all season tires poor performance in winter.
The Falken tires actually do quite nicely in everything but snow. I took the Boxster to West Virginia with the Falkens and we got a fair amount of snow, I thought I would never make it out of the state. I did not realize how bad they were when I stopped on a hill and could hardly get going again.
Pretty scary stuff, two-lane mountain road, no place to turn off and park, yikes. Even though we do not get that much snow in Central Virginia where I live, I am now looking for a set of snow tires for this winter and am open to any recommendations.
Ed
