Hello dear people. I cleaned my summer tires today and I noticed a crack in the tread of the tires. As it is difficult to describe it all, I took pictures of 3en of the 4 tires. All 4 tires have these cracks. Apparently they are only superficial and not even 1mm deep. The “Rille” where the cracks are located is exactly in the middle of the tread. It is about the tires: Firestone Firehawk. Size R15 185. Made 14-2008 and I only drove 7816 km with it What do you think about it?