Mechanics, junkyards and sometimes even tire shops will sell tires that are used but still have plenty of tread and are not showing signs of obvious wear as an alternative to consumers who experience sticker shock over replacing their worn tires. It's not uncommon for these tires to be priced at half the cost of new, and sometimes less. Tire shops and mechanics may also sell tires that are brand new but manufactured more than a year ago at small discounts of 10 percent to 15 percent. Discounts will vary widely depending on the tire's age, condition and type, and the business selling the tire, among other factors. No matter how appealing a discounted tire may be, consumers should be wary about buying either gently used or older unused tires. While they may get a great price, that savings could easily evaporate if these tires fail, causing a car accident that in turn raises auto insurance rates.
Tires are made of rubber compounds, which age over time even if they are unused or barely used, but there is no agreement on exactly how long tires can provide safe transportation before the rubber deteriorates to the point where it fails. Automakers' and tire manufacturers' recommendations for tire replacement, regardless of wear, range from five to 10 years, depending on the conditions. Exposure to heat, sunlight, humidity and salt air are just a few of the factors that affect how quickly rubber compounds in a tire break down.
Due to these issues, it makes good sense for anyone buying tires, even consumers buying brand-new ones, to check when the tire was manufactured and consider refusing any tire that was not manufactured within the last year. The problem is that determining the age of a tire isn't easy. Tires manufactured after 1999 have a four-digit code on the sidewall that represents the week and year the tire was made. For example, a tire with the code "DOT 4211" was made in the 42nd week of 2011. Tires manufactured before 2000 have three-digit codes that are more difficult to interpret. These codes are sometimes found on the inner sidewall of the tire, making them difficult to see if the tire is mounted on a car.
The biggest problem when buying used tires, even those that appear to be brand new or in very good condition, is that you don't know their history. Their life span may have been diminished in numerous ways such as by hitting curbs or potholes, getting punctured, becoming exposed to high temperatures or enduring harsh weather. Since the safety of a car and its occupants is in part dependent on the four tires it rides on, it seems like buying used tires to save a few bucks may be far more costly in the long run.