Been in the tire failure business for 20 years
Buying junk yard tires is a crap shoot. Maybe the car was in a serious accident and the tires were crushed. They may look great, but if you look at them under an x-ray you will see the busted belts and broken body plies. Sometimes the wrecker tows the vehicle with the tires under inflated tearing the sidewall plies apart. You have to ask yourself this, why would anyone sell a perfectly good set of tires if there was nothing wrong with them? If they sold the vehicle and had an extra set, then maybe their good. Junk yards, there is no history behind the tire. Carefully inspect the inside of the tires if you decide to buy them. No openings, cuts, scraps, loose wires or exposed body plies can be seen. No repairs accepted at all! Look at the interior for dark bands on the sidewalls, discoloration from high heat, anything unusual. Look for a nice clean shiny interior surface. A dark chalky interior is a sign of heat buildup. Look for usual wear on the tread especially in just one location, could be internal separation.