Well after 4 months it has come time to change my rear tires because one is pretty bald and the other one... well it sort of decinigrated on the highway yesterday. The question being I have KDWs up front which are fairly new and looking to try to put some F1's down back to see if they might last longer than four months.. would there be any problem having one brand of tires in the front and another in the back or should I just stick with the KDWs all the way around.

 

no problem, but mixing tires may give you funny handling characteristcs

 

I agree. Mixing tires is not going to hurt the car but the handling can suffer. Especially if the tires are side to side different. The performace is always going to be the best with the same tires front to rear. You want the same level of handling on both ends of the car.
If I can help let me know.