The Nissan GT-R tyres available at Tyres.co.uk include Dunlop SP Sport Maxx GT600 DSST CTT and Bridgestone Potenza RE070R RFT with sizes 255/40 ZR20 97Y for the front and 285/35 ZR20 100Y for the rear, for GT-R variants that come with these staggered run-flat fittings. Comply with the load, speed and run-flat specifications of the door-jamb placard.
You can find the Nissan GT-R tyre-size specifications on the Tyre and Loading Information sticker, located on the driver's side door jamb; this sticker is visible when the driver's side door is open. This sticker lists the recommended tyre sizes and cold pressure values for the front and rear axles. Be sure to confirm these against the sidewalls of your tyres prior to ordering.
Nissan GT-Rs don't always require four new tyres, however, all GT-Rs are all-wheel drive, and Nissan mandates matching specified fitments, brand, construction and tread pattern on all four tyres. If you notice some tyres have excessive wear, you have to replace all four. If only two need replacing, then you have to place the new matched pair on the rear axle.