Aging car tyres & DOT-code
With regard to the aging of car tyres, we follow the position of the Technical Information Platform for Tyre Manufacturers (TIP). This is an official advisory body of VACO that advises the General Board on technical issues. The following producers represent TIP.
Apollo Vredestein, Bridgestone, Continental, Goodyear Dunlop, Hankook, Michelin, Pirelli, Toyo, Yokohama.
Aging of tyres
The actual aging of tyres only begins after fitment/use. After 6 years of using, it is advised to have the tyre checked annually by a tyre specialist. We do not say replace after x years, but replace when serious signs of aging or damage occur.
Situation description and problem description
Before tyres are fitted to a vehicle, they are stored for shorter or longer periods of time. First at the tyre manufacturer’s premises and then at the distributor’s premises. The date of manufacture of the tyre (week and year) is marked on the tyre behind the DOT code. A consumer can therefore see when new tyres are fitted when this tyre has been produced.
Question to TIP
To what extent is a tyre subject to aging due to storage before it is sold and what is the influence of storage time on the condition of a tyre?
Advice TIP: Tyres are stored under optimum conditions at the tyre producer’s premises. This ensures that the tyres delivered to distribution are in optimal condition for a full life on a vehicle. The distributor also follows the industry guidelines for storage conditions, which are laid down in the document Recommandations of ETRTO. Tyres stored in compliance with these guidelines are virtually unaffected by ageing and are therefore in the best possible condition when fitted to a vehicle. During storage a tyre is unloaded, not inflated and only subjected to minimal temperature fluctuations. Therefore, the storage time before a tyre is fitted has no real impact on road safety.
The actual aging of a tyre does not begin until the tyre is put into service. Aging is affected by maintenance and use after fitting to the vehicle.
- Influence of storage temperature and storage time versus normal use(*)
Studies on the influence of temperature and storage time on the chemical process show that a tyre that travels 60 mph over 12,000 miles (97 km/h over 19,000 km) ages as much as a tyre that has been stored for 17 years at a temperature of 70ºF (21ºC). The influence of the storage time is therefore negligible. In other words: a tyre that has been in use for one year on a vehicle ages just as much as during 17 years of storage. Or: 3 weeks of use corresponds to one year of storage. This applies to a well-maintained tyre.
- Influence of storage temperature and storage time versus undervoltage operation(*)
At 35% under-inflation the temperature of the tyre rises to 80 degrees. A tyre ages 63 times faster than during one year in storage. In other words, a 35% under-inflated tyre will age in one week of use just as much as a tyre stored correctly for one year.
- Influence of storage temperature and storage time versus high operating loads
After fitting the tyre, the life of a tyre becomes totally different. From that moment on, the tyre is subject to the influences of high loads such as braking, steering, deformation, under-inflation, speed, road impact, high temperatures and the influence of sunlight. All these influences are not there during proper storage. Even when the vehicle is stationary, the tyres are in use as long as they are inflated and underneath the vehicle.
The influence of the storage time has a negligible influence on the technical characteristics of a tyre. The tyre ages during use, not during storage.
(*) R. G. Altman, E. M. Beutler, J. T. Kohler, “Erroneous or Arrhenius – Potential Impact of Oven Temperature Variations on Laboratory Aging of Tyres”, submitted for presentation at the 2009 Tyre Society meeting, and for consideration for publication in the journal Tyre Science and Technology.
You can tell the age of a tyre by the DOT-code
On the side of your tyre is a so-called DOT code. The last four digits behind the letters ‚DOT‘ tell you when a tyre has been produced. The first two digits indicate the production week, the last two digits the year.
An example: 1717 means that the tyre was made in week 17 of 2017.
Are there only 3 numbers on the tyre
Then this means that the tyre is from before the year 2000. Are your tyres six years or older? Then it is safe to have them checked every year. Do you doubt the age of your tyres? Feel free to ask your VACO tyre specialist.