If the tires sit for a long time, they might have some coloration issues. This is an extreme example, but if the tire sat in a puddle for a long time, you might find a water mark on it. Rubber doesn’t respond well to scuba diving, and the wet section of the tire will dry rot more quickly. If one side of the tire is lighter than the other, it probably sat in the sun for a long time. That means that it will chunk faster if you want to use it off-road. Also, look for greasy residue on the inside of the tire that could indicate oil or grease leakage (rubber doesn’t like oil), as well as on the outside of the tire, which might indicate obsessive Armor All usage. While we haven’t had tires around long enough for either to cause issues, many swear that these are among the worst things you can do to tires.