The OEM is a 255/35... If you go with either the 245/35 or the 265/35, you'll be 1.10% different in overall size. Of course, the 245/35 will be smaller, so at an observed speed of 75 mph (speedo reading) your actual speed will be 74.2. With the larger 265/35, you'll be doing an actual 75.8 mph.
That being said, each size is really close. Personally, I went with 245/35 all around as I wanted a square setup and didn't want to try to fit anything bigger up front without having to do fender mods...
I don't think you would have any problem running the 265/35 out back. You're talking 10mm... Not that much...
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