I am afraid to chime-in given the passion of the tire conversation ....not to mention my straying from the Porsche recommended winter tire. I have a Cayenne S up here in Alaska where there is SNOW SNOW SNOW. I have the summer 19'' oem rims and have just got the 18'' oem wheel to put winter tires on. I am going with the Pirelli Scorpion Snow and Ice stud-less winter tires because (1) I like Pirelli (2) I got good feedback on this tire for snow traction. I also looked into a possible studded snow tires which I have been using in Alaska for years on previous cars.....Nokian has told me their new Studded 18'' tire will fit...but I am going to try the Pirelli stud-less and hope that I don't fly off into the Cook Inlet........AK