Join Date: Apr 2011
Location: montreal canada
You mentionned YOKOHAMA previously....3 weeks ago i put new YOKOHAMA Avid Ascend (225-50-17) on my G6, 08, 3.5L. There new model of 2012. Extra silent , excellent on dry and wet pavement. They touring tires or summer tires if you want. No good at all in the snow (living in Montreal i have also 4 snow tires). Treadwear of this model is 740 . Look at this indicator cause it's give an idea of the lifetime of the tire (also depend how you drive) Paid 720$ -installed and my pressure sensors calibrated from a small shop of a friend of mine. This model is available for your size 225-50-18 and fit for 7 inches rim.
Since 18 inches tires are more expensives than 17, you should add at least an 100$ for the whole set. But again, lower is treadwear number, less milleage you gonna do with the tires. I wouldnt buy a tire with a treadwear lower than 500. Low numbers mean soft gum-mean tires could last maby only 20 K M. So in paying more, your tires could at least twice. If you oriented your choice for american tires, again,look at the treadwear.
Good luck and hope you wil find what is more suitable for your car