William, I had sidewall cracks that your describing on my last set of Michelin Tires and the tires were 10 years old. I went to Michelin Tire Care website and what they described about sidewall cracks told me that the sidewall cracks were not dangerous. I drove 1,500 miles home constantly checking the sidewall cracks and had no problems. Sorry, I can't remember perimeters of the cracks you will have to go to there website. When I got home, I had a new set of Michelin tires installed on my RV and I used the FMCA, Michelin Fleet Tire Program to purchase my new tires.