For early indication of tread seperation, check the base of tread pattern from the side wall for cracks.
How do I know this? I have a Ford Explorer, before Ford replaced those dangerous Firestone Wilderness AT tires, I could see a lot of cracks developing on those tires.
99 BMW 540i 6-speed 110K Km
03 SAAB 9-5 wagon 80K Km
92 400E (Sold) 245K km
Still missing the days with the Benz, it kept me busy.