I had a rear tire with lots of tread on it throw the tread and steel belts off at 60 mph. The tire still held air. As the belt and tread came off in one piece it whacked the tail light and tail gate and damaged them both. It had a good 1/2 to 3/4" of tread, but the rubber had stress, oxidation cracks all over the tread area, in the groves between the tread, that I had not noticed.
The trick is to check the tire sidewalls and tread area for stress cracking, no matter how old it is.