I have the 2009 Sierra wheel that came on the all-terrain package....and it's an 18" wheel. Love the wheel! Time for new tires. Should I just stick with the factory size, or look to maybe plus size it?? Was thinking maybe 275-65-18? Didn't want to drop the side wall lower than a 65 series. The Bridgestone dealer suggested going to a 265-70-18....but that's like 3/4 inch taller and no wider...but for some reason that size is almost $100 cheaper on 4 tires compared to the stock size. Thanks in advance for your input.