How to check used tires?
One time a guy tried to sell me a tire with a nail, his explanation was, that is why it is cheep. I did not buy it
Look for the obvious, cracks, cuts, batches. Batches on tires are okay if it is done right from inside the tire with a reliable tire technician.
One time I was at a tire shop to dismount some tires to get the rims out, the technician was funny; but not on the things I like to joke a bout it, when he found a nail in one of the tires, it was easy enough to take it by hand, he through out in the street and said make good business. I do not drive there very often now.
Also look in the area where rims and tires meet, tire bead, this is a killer area, if it has been damaged, that said, no fix, the tire worse zero, you will pay money to disposal that tire and do not try to put a very used tire has no tread, it will cost you installation fee, will end up no saving at all And it will give you hard time with the rain on the ground. You might find the car or the truck sliding, and you think, will we do not have snow, what happened? What happened is, no way for the water on the road to go; but when you have a tire has good tread water can slide in between the tire tread and then you have good traction.
One time I met a customer buying a set of p235/75r15 for his van. It was not only he has no tread, I can see the steel wire under the tire robber. The good thing is he bough the set for a very good price. !