I would recommend COSTCO.
Since you buy a set of four, you enjoy the following:
1. Free rotation and balancing for every 10,000 KM (any garage will charge you at least 25 CAD)
2. If you have flat tire, COSTCO will fix it for you FREE. (Any garage will charge you 15 CAD)
3. If your tire is not fixable, COSTCO will replace one for you, you just have to pay the amount equivalent to %age of tire worn out. I.e. if you tire has 70 % left, then you have to pay 30 % of the tire and you have a new one.
4. The above can be done in ALL Costco in Canada, as long as you have the original receipt with you.
** I bought my tires in Toronto, and I have a flat tire which cannot be fixed, I went to Ottawa Costco and has that replaced, that was five years ago.