You know how your car’s age, but do you know how old its tires are?
Knowing the age of the tires on your car could mean the difference between a fun and safe trip to the beach and a family tragedy. Safety researchers have looked at tires that appear fine, have plenty of tread life left on them and show no outward sign of deterioration. Yet these tires experienced catastrophic failure that resulted in terrible accidents. The common denominator in each case was that the tire that failed was at least 6 years old. They may have appeared to be “new” or even recently installed on the car but each tire was at least six years old from the date of manufacture.
The industry, through its trade groups, have denied that there is a problem and have resisted efforts to put expiration dates on tires. However, car makers such as Volkswagen, Toyota, Ford and many others realize a problem exists and have included a warning in their owners manual to replace any tire older than six years no matter what its tread depth may be.
The problem with old tires is that they have a tendency to just come apart. The tread suddenly and without warning will separate from the body of the tire. At highway speeds, this is a formula for disaster, since the driver will often be unable to control the vehicle. If the tire comes off the rim, and the rim then digs into the road surface, it creates a pivot point that can result in the vehicle spinning or rolling over. This is a hidden defect that the ordinary driver will never be able to discover by examining his or her tires.
You should not assume that a new car or a new set of tires are fresh. Tires often sit in warehouses unsold for extended periods of time. This may be especially true if it is an uncommon tire size. Research indicates that tires degrade even if they are not in use, so that an old spare tire or a “new” tire that has been sitting on a shelf at your dealer for 6 years may be just as dangerous as the tire that you have been driving on.
It helps to understand how a tire is made to understand why it degrades after 6 years. A steel belt tire is made of several component parts including the inner liner, two polyester body plies, two steel belts, two bead-reinforcing strips, the sidewall structure and finally the tread. Once these parts are assembled the tire is loaded into a tire press for vulcanization, which is a process that that fuses the component parts together under extreme heat and pressure. Over time that vulcanization process begins to deteriorate as the component parts dry out and air permeates the inner liner causing the parts to begin to separate. All products have a useful life. Most of us have an expectation that the fatigue life or its useful life should always exceed the tread life by some margin of safety for all reasonably foreseeable uses and conditions. Sadly this reasonable assumption is not true.
You can determine the actual age of the tire.
There is a Department of Transportation Code number on every tire, although it may be hard to find and decipher. This code number is a combination of letters and numbers that can reveal a lot of information:
- The number should begin with “DOT.”
- The next two characters indicate the manufacturer; the next two characters indicate the plant where the tire was made.
- The next 3 or 4 characters are optional and for the internal use of the manufacturer to record company specific information about the tire and are therefore only meaningful to that company.
- The last 3 or 4 digits tell us when the tire was manufactured. If the tire was made before the year 2000 the last digit tells us the year of manufacture and the 2 digits before the last one tell us which week during the year. So if the last 3 digits are 125 we know that that tire was produced during the 12th week of 1995 or 1985 After 2000 4 digits are used in the code so that if we saw the numbers 1205 we would know that that particular tire was produced in the 12th week of the year 2005.
Most consumers have no idea of the hazards posed by old tires. We happily drive off assuming that if there is adequate tread there is still life in those old tires. No matter what the life of a tire might be under ideal circumstance, no tire exists in ideal circumstances. That is particularly true here in Florida where many of us live in coastal areas with a high salt concentration and all of us deal with the intense Florida heat. Old tires come to us in many ways - it was a spare for a long time or maybe we just don’t drive a lot, from a dealer, swap meet, flea market or even online. If the tires look good, few of us would ever question when they might have been manufactured.
The tire industry makes little or no effort to educate the motoring public of the hazard of aged tires. In fact, when their products fail and cause injury their response is to blame the consumer by claiming improper maintenance, bad repair, under- or over-inflation or exposure to road hazards that caused tire failure. The DOT Code number is unknown to most consumers, and how to decode it is known to even fewer. The DOT Code was never meant to act as a consumer warning. The consumer has never been provided with an adequate warning of the dangers posed by the use of old tires and in fact the industry itself has never been able to agree on a uniform standard relating to when a tire should be taken out of service. Most independent researchers agree that the older the tire, the higher the chance of failure, and 6 years seems to be a sensible line of demarcation to replace aging tires.