Per an article from Tire Rack.com (a large well known/respected US online tire/wheel shop), the "Nx" tire ratings are from Porsche, and basically just designate different itterations of a given "Porsche approved" tire. Taken from here:
http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=26
Production tires that have passed all of the tests and received the engineering department's release can be branded with an N-specification. The N-specification brandings include: N-0 (N-zero), N-1, N-2, N-3 or N-4. These markings on a tire's sidewall clearly identify them as approved by Porsche for their vehicles. The N-0 marking is assigned to the first approved version of a tire design. As that design is refined externally or internally, the later significant evolutions will result in a new generation of the tire to be branded with N-1, N-2, N-3, etc., in succession. When a completely new tire design is approved, it receives the N-0 branding and the succession begins again.
My bad , from the earlier post regarding my "suggested" tire ratings.
https://www.gtplanet.net/forum/showthread.php?t=64932
http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=26
Production tires that have passed all of the tests and received the engineering department's release can be branded with an N-specification. The N-specification brandings include: N-0 (N-zero), N-1, N-2, N-3 or N-4. These markings on a tire's sidewall clearly identify them as approved by Porsche for their vehicles. The N-0 marking is assigned to the first approved version of a tire design. As that design is refined externally or internally, the later significant evolutions will result in a new generation of the tire to be branded with N-1, N-2, N-3, etc., in succession. When a completely new tire design is approved, it receives the N-0 branding and the succession begins again.
My bad , from the earlier post regarding my "suggested" tire ratings.
https://www.gtplanet.net/forum/showthread.php?t=64932
