I've had these indentations on most all tires I've ever owned. Camping last weekend, my Nephew pointed to one of my tires and said.... "I don't want to scare you or anything, but is that a problem?" It was just the same indentation I've seen for years. I then pointed them out on my truck tires and then on his!!!!!!!
BTW ..... Carlisle tires are guaranteed for TWO years. I wish they made better tires ... but I can tell you, if you have a problem .... they do seem to take care of you. Watch out for cracking on the sidewalls!!!!!!