I'm thinking of changing from staggered tire setup to same size on all four corners. The idea is to reduce understeer and extend tire life by rotating. Has anyone experimented with this and come up with a satisfactory set-up? I'd buy new wheels so there are a lot of possibilities.
I think your desired understeer correction will be less than ideal even with a non-staggered setup. I had the original M sport 17" five spokes for a long while with 255 rubber at all four corners and it helped a bit. I now am running M5 wheels (18") with 245 in the front and 275 in the rear and I'd say the overall balance is the same. There is more grip at the rear now but when pushed hard the vehicle will still push in the corner until your right foot helps out. Neutral balance is tough to do in a 4000 pound sedan but this car is pretty good even against some tough standards.