Michelins crack. It's that simple. Two people I work with fought them over this...both wound up throwing away tires with plenty of tread because they were rotting off the rims! Both were accused (and it MOST EMPHATICALLY was an accusation) of using tire shine (neither did). Basically, Michelin stridently claims they have NEVER made a bad tire, and whatever happens is your fault! Neither will ever deal with Michelin again under any circumstances.
I will run four different used Chinese tires before I will run Michelins.