With PagodaFest fast approaching, it is important to be sure our cars are in proper and safe condition. I expect there will be SL’s which have spent much time parked in a garage and probably not seen many recent miles over a number of years. For this event, these cars may be required to drive high-speed freeway miles in a short few days.
Specifically, please check the age of your tires! Any tire which has reached approximately seven years old, should be replaced (some sources say ten years, but that is pushing it). I have seen way too many gorgeous classic cars suffer severe fender and structural damage from tread separations and exploding older tires. In the old days, having a low-mile, always garaged tire with no sign of sidewall or tread deterioration or cracking meant you were good to go. This is no longer true with newer steel-belted tires! Age becomes a primary consideration beyond visible rubber condition, storage or miles.
In the old days, tires were constructed with fabric belts. These belts were molded firmly into the tire and would only be a problem with rubber cracking which allowed oxygen to deteriorate the fabric. In the “old days” a tire would most commonly blow out a sidewall, and sometimes a location on the tread itself and then it would quickly lose air. Again, this was generally trackable to the age of rubber and cracking visible on the surface.
Things are different today with our steel-belted tires. The steel belting does not bond as well to the inside tread rubber as did the fabric cords of days past. The constant pressure of tire inflation is continually and slowly pulling the steel belt apart from the inside rubber it was originally molded to. Industry estimates that after seven years of “in-use” time (in-use time is defined the time a tire is inflated with air pressure and has nothing to do with miles driven or how it is stored), a tire has lost 40% of its strength, or more.
When these older tires are exposed to higher speeds, the chances of a dramatic tread separation goes up exponentially as compared to a newer tire. This separation is not just a loss of air (like would have been more often experienced with an older fabric style tire). The tread separation can be sudden and can cause major fender and structural damage as well as a potential loss of control.
And yes, that beautiful, crack free, fresh appearing, original spare which has always stored in the trunk under pressure (since 1970?) is a tread seperation ready to happen. I have seen these types of spare tires shred within 10 miles of being installed.
You can read the date of manufacture of your tire per its DOT code on the sidewall. Tires made after 2000 have a four-digit date code (see picture). This code was imprinted only on the inside of the tire sidewall until approximately 5 years ago when it was placed on both sides. A three-digit date code means the tire was produced somewhere before year 2000, but you have no way to know which decade it was made? If you find a three-digit date code, the tire automatically too old and must be replaced!
Take the time to verify you have safe tires, please. It is not worth a tire explosion to ruin a trip. Tires are not all that expensive compared to what you can lose.
