I have coupe 18s on now with the stock 245/40 225/40s and I dont like the bigger side wall rear. Is it uncommon for people to go all 225/40 around or is there a better size to go with. I like all to be the same and its a plus to be able to rotate

 

I'd go 235/45 18 all around - it's the same diameter as the original 17" tires on the sedan, so there will be no issues with the speedo or VDC. There are good choices now in that size. I'm running the General GMax AS-03s and like them a lot.