Greetings:

I own a 2011 audi a8 and I'm due to get a new set of tires and my current setup is 265 40 20 .....theres only 3 or 4 type of tires in that size was wondering if go 275 40 20 or 255 40 20? a friend of mines said i can't switch sizes. I did a few searches but not for a A8 answer was found.