How long do tires last?

If you have a collectible car, the tires may look new, yet be falling apart inside. The culprit is dry rot, which destroys tires from within. Dry rot causes the rubber to break down, become weak, and eventually fail. Usually without warning.

Dry rot is the visible manifestation of the natural process of rubber breaking down. It’s accelerated by a number of factors including:

Ozone exposure;
Exposure to bright sun and heat;
UV exposure;
Use of certain tire dressings and chemicals;
Underinflation.

Dry rot is a bigger problem in the south because it’s hotter and the sun is brighter. It’s a problem at high altitude because the sun is more intense and there is more UV exposure.

Some people say tires need to be replaced every five years in the tropics. Others say tires should be replaced every ten years, wherever they are. Then there are those who say you don’t need to do anything unless you can see dry rot attacking the tires. I think that last opinion is probably closest to the truth, because I see cars that are stored indoors all the time, and the tires look perfect after ten years, but other cars that are parked outside in the sun every day show dry rot damage in three years.

That leads to a question – how do you know the age of a tire?

Tires that were made after January 1, 2000 have a code stamped on the inner sidewall that begins with DOT and ends with four digits molded into the tire. The four digits indicate the week (1-52) and the year (00 for 2000) that the tire was made.