You can do it, but the rear tires will be seriously stretched, and a bit silly looking. As stretched as they would be, you'll also lose a bit in the diameter. It will appear as a larger gap between tire and fender, perceived and actual. Some do this as a winter setup, but that's not the same in spirited driving, and I wouldn't do it if I were you.

 

245 will fit the rear too. I run 245/40/18 on my staggerred 124s for winter.