The next race my co-driver ordered us up two new Bridgestone RE-71R so we went to the new lightweight forged 18x10.5 wheels and the 275 RE-71R on all 4 corners. The result was fairly remarkable.
Im a big fan of not overtiring! and I'm glad thats working well because thats my target size wheel and tires ;-) I presume you are spraying those stones a good amount between runs?