If you are running 17" rims, the next size up is 315's!(if you are talking about the drag radials) Here is a pic of the 315 Nitto's mounted on my 17x9 cobra r's...
Got them on today and they are 1/2" wider than the GS-Cs in the same size. Boy do these things hook up The traction is better than any other tire I have used before and I have used everything but Handcooks.