One of the best dual duty Extreme Summer tires out there is the Hankook RS-4. 265/35-18 front and 285/35-18 rear was a very popular configuration amongst E9X M owners, however, it appears Hankook discontinued the 285/35-18 size
.
Our two other favorites in this Extreme Summer category are the Dunlop Direzza ZIII and Bridgestone RE-71R (faster, but wears much quicker in comparison to the other two), but they only offer a 285/30-18 which is a bit too short out back.
Your best bet is to run the Michelin PS4S (265/35-18 / 285/35-18) and to install adjustable camber plates so you can dial in some negative camber. Not only will negative camber prevent you from roasting the shoulders of the tire, you will improve turn-in and grip throughout the corners. Adjustable camber plates pay for themselves quite quickly and we would suggest approximately -2.5º up front, and -1.8º in the rear.
If you get a bit more serious about tracking the car, we'd strongly recommend switching to a rotatable square setup (18x10" ET25 or 18x10.5" ET22) with 275/35-18 tires. In that size, you have a ton of fantastic extreme summer tire options, as well as r-compounds once you make the jump.
- Ryan