On Porsche's website they use Goodyear Ultra Grip tires in the photos for their winter wheel and tire sets.
19 inch wheels
Front axle: 9 J x 20 RO 54 with 245/45 R20 103V XL tires,
Rear axle: 11 J x 20 RO 60 with 285/40 R20 108V XL tires.
20 inch wheels
Front axle: 8 J x 19 RO 50 with 225/55 R19 103V XL tires,
Rear axle: 10.0 J x 19 RO 47 with 275/45 R19 108V XL tires.