macca993:
Again Peter, at least in the UK and Down under a manufacturer cannot dismiss a warranty claim for fitment of a non OEM part unless that part itself is proven to have created the claimed warranty issue. Porsche recommend a specific tyre for the GT3 but you wont get refused a factory engine warranty/recall claim because your Porsche has N rated tyres not reccomended for the GT3. Most of us taking this car to the track here and in the UK will probably rip off the expensive Michelin skins and replace with Hoosier and Hankook 214/221 or Toyo R888 as soon as the sizes and fitment are available from those manufacturers. Lifes a bit too short to be worrying about wether Porsche like my new R compound track tyres as Im ripping around at track at speads up to 250k pph un insured LOL!
As far as I know, EU law forbids car manufacturers to oblige the usage of a certain tire BRAND. Only the size (width, etc.) and type (speed index, weight index, etc.) needs to be the one approved by the manufacturer of the car.
I do not worry about people using a non N-rated tire on the track (even if I would be careful at the beginning since there isn't much experience yet from "older" GT3 cars because of the new all-wheel steering and our sources indicate that the new all-wheel steering is very tire "sensitive") but on the street and especially at the limit.
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RC (Germany) - Rennteam Editor Porsche 991 Turbo S (Sept. 2013), Cayenne GTS (958), BMW X3 35d (2013)