Costco Tire Center

I purchased 4 new michelin tires in 2011. In 2014 (only 3 years later!) I noticed dry cracking on all tires especially near the rims at only 14535 miles on tires. Went back to Costco demanding tires to be replaced free as they were obviously defective. They refused to replace free but stated they would credit me 75 % on the cost of new michelin tures. I left there without any changes. I returned to Costco again in 2015. By now the tires were really badly dried cracked at only 21000 miles of use. I asked for free new tires again. They offered only a 60 % credit on new tires. I refused offer again. I asked them to rotate and balance the tires as per the contract of 2011. I was told that the tires are are so dried and cracked that they are NO LONGER SAFE to drive and they refused to do any contractual service on these tires. I left without any sadisfaction again. The tire center managers are rotated with the warehouse cashiers etc. They are slow workers and some are rude. Keep an eagle eye on them as they work on your car. Do not leave to go shopping! Today may 22, 2016 I will try once more to get my money back for the garbage tires they sold me. I am not saying that michelin tires are garbage, but simply that I received a set of michelin tires that are definitely defective in material and/or manufacturing!