tread

I am trying to learn more and understand the tire tread and depth on these incredible machines. I have a TR 2015 Z51 with 20,500 miles on it and came out 2 Saturday's ago to a flat tire on rear passenger side.....I still had stock tires on. Took it in to Classic Chevrolet in Grapevine (DFW area)...

Just returned from a 8700 mile road trip and was rotating tires and found both back tires with steel showing on inside like there was something that rubbed the tread off. Checked both and found nothing that could have caused this abnormal tread wear. Anyone else experience this issue? Any...