Porsche Club of America - Upper Canada Region: 35th Anniversary September 2011

You should have received a tire guide from Porsche Cars Canada in a recent issue of the UCR PROVINZ newsletter. This guide detailed which brands and sizes of tires have the factory 'N' approvals for use on your Porsche.
As long as the tire you're buying has this 'N' stamped on the tire you should be fine, regardless of the source of your tire purchase.

If I were your local Tire shop and were charging $100 more than Costco, I'd give you the same story. Costco buys in huge volumes and works on very low margins. That's why they can sell the tires for so much less. I don't hear anybody claiming that the tires sold at the Tire Rack are made to different standards.

Buy with confidence, Costco & Bridgestone will stand behind your purchase and I'd almost guarantee they are exactly the same as those at your Tire Store. Regardless of where you buy, check the date codes on the tires (before they are fitted) as that is of much more concern. It is important that they are all of the same vintage and not more than 1 year old. http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=11

Unless you are major concerned about your lap times at the Nurburgring with your Porsche, don't get too hung up about having tires recommended by Porsche. While the car is within the factory warranty period, maybe, but let's face it, they are tires, they keep the rims off the road. What more do you need!