I need some help figuring out the brakes. I have a 2009 Cadillac cts Awd 3.6 Premium Model, and I wanted to buy some Power Stop Brake Kit which comes with rotors and pads, now there is two types 315mm or 345mm. The model I am looking at is Powerstop K4135 apparently.this is the.345mm kit with 13.58 in front rotors and 13.386inch rear. According to summit racing employee.he told me it wont fit the.AWD MODEL only rwd. Can you guys shed some light for me as I have no clue if my brakes are 315mm or 345mm or can I upgrade to these with.no.issues. The car has 18" performance wheels and tires from factory. Any help would greatly be appreciated.