I noticed some new cracking or "checking" in the rubber at the bottoms of the tread grooves on the date coded 3107 Perelli P-Zero Neros that were OEM on our '08 Mustang GT. We got the car last June, tires were easily 1/2 still there at 22,000 miles, but they had no cracks then. Since then, they've worn some and developed cracks in all 4. No more Perelli P-Zero Nero s for me.
Now it has 26,446 miles, and I don't want to risk damage to a rim (not scared of a flat, I've had a few and some at "extralegal" speeds
) so Friday, I got her up on stands and pulled the wheels and loaded them in my PU along with 4 GoodYear Eagle RS-A tires I had set aside and carried them all to a buddies and we swapped them and balanced them and all is well again.
These are tires I know I can trust.