I'm guessing my new GT will have the same Pirelli Nero Zero tires that I've seen on the ones in the lots. Just curious if they are "R" or "ZR"

The details the dealer has online shows 235/50R/18. But every 5.0 GT Premium I've seen has the ZR tires. I know mine is supposed to have All Seasons on it.

Anyone know? And what is the difference between the R and the ZR?

 

you are missing part of it. The "R" is for radial or radial tire. The "Z" is a speed rating or a Z radial but after the tire size on the side of the tire will be more info the load index and the speed rating. example:

235/ 50ZR 18 95Y or for the all season 235 50R 18 97W . Concern yourself right now with the numbers I have in bold. The summer tire is a Z rated tire and has a basic speed limit of 149mph but a "Z" Y tire is rated for 186mph but of the "Y" is put in parentheses like this (95Y) on the tire then it is in excess of 186mph. The W is rated for 168mph. the 95/97 numbers are load numbers. ZR rated tires would have a Z, W, Y or (Y) rating then it goes down to V, H and lower but these are not Z rated tires.