Pirelli doesn't make the Trofeo R in proper sizes for the 918, nor the LaFerrari, nor the P1.

918 has 265/35-20 325/30-21

LaFerrari 265/30-19 345/30-20

P1 245/35-19 315/30-20 (proper designed sizing)

The Trofeo Rs that the P1's been running are sized for the 12C/650S, 235/35-19 305/30-20. 

The Cup2s, on the other hand has 7 out of the 8 sizes mentioned above, Michelin doesn't make a 315/30-20, but they do have 305/30-20 and 325/30-20. 325 might be pushing it to fit the P1 though, with Race mode dropping the car down, all the volume inside the wheel well will be gone. 

Maybe some enterprising individual who have access to all 3 cars can call up Michelin and ask for Cup2s all around and compare the cars. 

But even then it still won't work, the 918's Cup2s are designed for the 918, the GT3RS wears the same size rubber but those Cup2s are structurally different and have different compounds also. I believe the LaFerrari's certified Corsas are also different than the P1 certified Corsas. Apples to oranges comparison again.

The only fair way to compare is to wear the factory certified rubber, if the tread and compound gives one car a clear advantage or a clear disadvantage, then so be it. Blame it on the factory for choosing the wrong kind of tire. 


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