Both Sam's Club and Costco offer private-labeled tires that only they sell. The tires are made by the big mfrs but have a model name different than their normal product line. These can be great values, and it's what is typically stocked at the clubs. But only the club you bought from can warranty the tires. Obviously, any store can take care of you but only that club. So if you bought, say, a Goodyear Allegra from Sam's, only Sam's can provide warranty service. If you take it to a normal Goodyear retailer, they can't help you since they don't carry that model.
Depending on the car and tire, sometimes the best place to buy tires is at a national mass merchant like WalMart of K-Mart. Don't laugh. There are hundreds of stores nationwide. If you have a tire problem any store can help you. Something to consider if you tend to drive long distances.
But many times the best place to buy is from a local independent shop. You can get to know them, see their equipment, watch how they handle other cars, and most of all, be able to count on them if you have a problem.
The big problem I have with buying from an online retailer is what do you do if the tires you bought are defective or have problems like being out of round? The amount of time and money you'd spend installing tires, removing them, shipping them back to the online merchant, and reinstalling them will prolly kill any savings. And no one locally has an incentive to help you out since you didn't buy tires from them. They'll take care of their own customers first.
I'm not saying, <strong class='bbc'>don't buy online[/b]. Just consider all the options instead of just the price.