I'm running 2 different sets of tires on the front and back right now as well and I agree. I'm running Kumho Supra Ecsta 712's on the rear. 245/45/16's and on the front I have some POS Michellin Eagle GTII's with like 20% tread. It's safer to run your better tires on the rear but no matter how you set it up you can't fully push the car to it's max without all 4 tires the same and decent rubber all around.