OK...I'll bite on this....
They are 275-40-20 P Zeros rear and 245 45-20 on front in case you were wondering although that is all the magazine articles.
Pro:
1/ The ride that this car offers over rough pavement is bordering on extraordinary. Creamy smooth and no wallow. Combo of great suspension tuning and good tires choice. I think GM chose a taller tire than a 30-35 profile to give a little more refined ride over the crap roads all over North America these days. Non run flats help here of course as my Run flats on my C5 Vette were just a horrible tire.
2/ In the rain they STICK....
3/ In the dry they STICK....
Con:
1/ I have read online (tire rack etc...) that they wear real fast
2/ Seems like an original Pirelli Size cause they are EXPENSIVE to replace. All of us with SS's better save our pennies now cause they are over 400 bucks US each from Tire Rack
3/ I could not find one value (Sumitomo, Falken, Kumho....etc) maker making this exact size for replacement....Maybe I missed something but did not see any....
Great tires....Great ride....Great stickiness....Get ready to bend over when replacing them.....