With every new generation of Porsche, the outer limit of grip are tested with heavier cars, larger contact patches, and way more power than ever before. In order for your new Porsche to continually improve, tire technology has to continue evolving to cope with the demands of the modern and more advanced Porsche. The company has been working directly with its tire suppliers to create the N-spec rating to confirm for Porsche owners that a specific tire has been approved to maximize the performance of their car.
Unlike some sports car companies, which simply pick a tire from a tire manufacturer's lineup, Porsche works directly with tire manufacturers from the beginning of a new tire's lifecycle, long before production begins. To be an OE supplier to Porsche, the final product must be jointly developed between tire engineers and Porsche's vehicle engineers. While dry weather grip is important for your GT to achieve its Nurburgring lap time, there is an equal focus on wet weather performance, as Porsches were built to be driven even in inclement weather.
The first, and perhaps most important metric for a new tire is its speed rating. The tire company will confirm that the new tire is capable of supporting the weight of the Porsche vehicle, the stresses of added downforce, and the incredible energy it takes to reach a Porsche's top speed. Then the tires are subjected to a barrage of additional tests, confirming the prototype meets Porsche's standards for road noise, wet weather grip, and dry weather handling. Durability is a top priority for Porsche, especially at speed.
Only once the tire has passed all of these rigorous tests, and the engineering department has signed off, can the tire be branded with an N-spec. New for 2019, N-spec tires will receive a specification based on which Porsche model line it is approved for. As before, the first letter will stay N, simply identifying the tire as N-spec. There will also still be a numeral from 0 to 4 which indicates which revision of the tire it is, with 0 identifying it as the original design and construction. New this year is a second letter wedged in the middle which identifies which vehicle in the Porsche lineup it's been homologated for. 911 models are NA, Boxster and Cayman models are NB, Cayenne models are NC, Panamera models are ND, and finally Macan models receive an NE specification tire.
Here is the update, as stated by Tire Rack:
A specification ending with the “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 new generations of the tire to be branded in succession. For example, the NA0 branding indicates the first version of a Porsche 911 Carrera tire design. Similarly, NC1 is the second version of a Porsche Cayenne tire design. When a completely new tire design is approved, it receives the “N#0” branding, and the succession begins again.
It is also important to know that while Porsche N-specification tires have been fine tuned to meet the specific performance needs of Porsche vehicles, the tire manufacturers may also build other tires featuring the same name, size and speed rating as the N-specification tires for non-Porsche applications. These tires may not be branded with the Porsche N-specification because they do not share the same internal construction and/or tread compound ingredients as the N-specification tires. Using tires that are not N-specific is not recommended and mixing them with other N-specification tires is not permissible.
As before, Porsche recommends replacing tires in axle pairs if they have more than 30% wear, and do not permit for mixed tire types on a single car. If the N-number of your tires has been discontinued, Porsche recommends replacing all four tires to the updated N-spec number revision.