Check the " DOT " date made on the side walls.A HAMB member posted a while back about his 40 Ford tire blew out at speed that he said looked like new but was over 7 years old.His wife was seriously injured in the roll over.After reading I checked mine and with 2,000 miles on them they had cracks all the way around at the inside bead. They say 7 years on tires they should be replaced.Food for thought!