I went today to Perilli and replaced the two rear tires with same size 255/45 ZR18 P Zero, (I think the numbers are correct), and kept the front Michelin. I only have around 20,000 miles on the 1999 740iL. thank for the advise. Fareed, Brian is correct. Check the tire type on the other rear wheel, & purchase the identical variety. Pilot Sports & XGTs are made of different rubber compounds and will have different handling characteristics. Either go with the identical tire, or if you decide upon the performance tires, change them all to the Pilot Sport variety. Simeon