Question about mazda 6 rims! PLEASE HELP!!!!!!!!!

Hi
I have a problem here guys and appreciate any help.
I own a 2003 mazda 6s.I changed the crappy factory rims for RX8 18 inch rims.I used to have tire size 225/40/18 Zr on the rims and they fit my car.I had them on for 32K. I recently bought new tires again this time I got greedy and got Flakens 245/4018 ZR . The guy at the tire store was telling me that There might be a problem with the 245 size.Has anybody gone that size for their mazda 6S? The issue is not rim size it is the clearance .I would appreciate any help.

The issue he's talking about is the clearance in the wheel well from tire rub.  With that size you're almost guaranteed to have issues unless you get them to roll your fenders.  Even then it's cutting it close but usually that's the simplest and cheapest solution.
 
D to the B

thanks. I asked the dealer and they said 235 will fit.not 245.