Problems with 2011 BMW 335d TIRES

i purchased 4 replacement run flat tires for my wifes bmw 335d with 40,000 mile tread wear warranty. after 20,000 miles the front tires were half worn and the rears were near bald. i contacted tire rack, where i had purchased replacement tires, and they sent out 2 rear replacement tires to their local installer; which i fully paid for pending return. upon installation it was discovered that the tires i had originally purchased from tire rack were not run flats but standard tires. the tires look from the outside exactly the same, bridgestone re960 vs re970s. there is a big difference in price and you are not supposed to mix non run flats and run flats. i contacted tire rack and they would not help. their customer service would not listen but blamed the problem on me or their installer. with some investigation i learned about dot numbers and was surprised that the installer does not track the dot number and only tire rack has. tire rack is the only one with the dot number and there seems to be no way to verifying the dot numbers. they say it is not their mistake but communication with them has been difficult and they dont seem to have a customer oriented or trustworthy culture. i spoke with the installer and they reviewed the labeling and segregation of the tires received from tire rack to prevent switching. they are a small installer and there process seems reliable. who knows how often this happens but i wanted to share this story with others so they buy their tires from the installer to eliminate this problem.