I was traveling at a high rate of speed on the freeway, when i heard a noise. as the noise got louder, i realized it must be a flat tire as the vehicle begin to pull in one direction. as the noise got louder i saw smoke coming from the back passenger side of vehicle. i pull over to find that the tire had completely separated from the sidewall. the tire was a continental contisport contact 255, 40zr 18, on a 2002 bmw m3. the tire appears to have simply blown out due to the separation. i believe this to be defective workmanship. i was told by the tire dealer that this is "common" for low-profile type tires. i do not think this an acceptable explanation, as the tire was not underpressurized, bare and/or damaged. i believe this blow out was due to a tire defect (tire separation). the only tire i could find to replace it was another brand. i will not put continentals on my car in the future. i do not feel safe driving on them since i do alot of freeway driving, and i wonder when one of the other tires will separate and blow out. *nm