SoCal RS4

Hi all. This is my first post here as I have just acquired a B7 RS4! The car came with some old rubber and I am now looking to buy a new set. After doing the due diligence on the consumer sites and spending quite a bit of time reading threads on the subject here, I have arrived at the Potenza RE-11 as the best choice.

Question: My tire store tells me that the Potenza 275 (width) will fit on the factory rims without rubbing (also confirmed on many threads here) but that the Bridgestone warranty will be invalidated because that rim is .5" smaller than the recommended rim size. Has anyone done this install and had issues with sidewall bubbling or roll-over? Other issues? I am asking because I really want the extra rubber that the 275 width would give me (not to mention it looks great).

Thanks -