a few things.....if they have 600kms on them it's possible the tires are from Japan. It's probably not a problem but sometimes cars can sit for a LONG in Japan, at the auction houses and on the docks and over time the tires go hard. Being a 96 GTR however (high demand), it's unlikely.
I don't think Maximamike's right about the wheels lighting up.... if they had enough magnesium to do that it would be freaky.... magnesium burns hot as hell.... it would be seriously dangerous. Also, if they had high magnesium content they would corrode very easily and fire extinguisher chemicals would break down the metal (if my chemistry of many a year ago is correct). All just fun info kids!