Choosing the right tires is not a small decision, and each driver needs information about the tire itself to support the selection. This is where the markings on the tire's sidewall come in. From the tire markings, you can determine, for example, the age and size of the tire. These are needed to determine if the tire is suitable for your car and whether your tires are already past their prime. One marking that puzzles many drivers is the so-called DOT marking or DOT code.
What is the DOT marking on a tire?
The DOT marking is found on the tire's sidewall and indicates the tire’s manufacturing week and year. The abbreviation DOT comes from the words Department of Transportation, referring to the United States Department of Transportation. It is required in the United States tire market.
How to read the DOT marking
The marking indicates the tire's age, manufacturer and place of manufacture. The first two numbers indicate the manufacturing week, while the other two numbers tell you the year when the tire was manufactured. For example, the marking 3023 indicates that the tire was manufactured in week 30 of 2023.
Pay attention to the age of the tire
How should the DOT marking then be interpreted? The DOT marking is important as it is indicating the age of the tire. However, age alone does not tell you whether the tire is still roadworthy or not, so it's worth keeping a few guidelines in mind to evaluate the age of the tire. These are also particularly beneficial when buying used tires.
- The total age of the tire should not be over 10 years from the date of manufacture. As the tire ages, its driving properties deteriorate, and the rubber compound becomes brittle. Therefore, an old tire is also less safe. The total age is calculated from when the tire was manufactured.
- If the total age of the tire is still under 10 years, its total service life should not be more than six years according to recommendations. However, there is no single recommendation for all tires, as the level of tire wear depends a lot on the driving style and how much the tire is used.
- When buying tires, keep in mind that tires can be sold as new if they are at most five years old. The markings on the tire's sidewall help you interpret its age.
- The marking of the tire's manufacturing date can be found only on one side of the tire.
The quality of the tire also affects its wear. Cheap but poor-quality tires wear faster than premium tires. Therefore, saving on tires may not be worthwhile in the long run, considering you may end up needing to purchase a replacement set of tires much earlier on. Paying a bit more for a high-quality premium tire can increase the treadlife due superior materials, craftsmanship, and low rolling resistance, so you can enjoy driving on it for longer.
So, remember: the service life of car tires is typically around 6 years in service or 10 years from date of manufacture, whichever comes first.
Other tire markings
The markings on the tire's sidewall are presented in a format such as 205/55 R16 94 V XL. This reveals the following tire characteristics:
- width
- aspect ratio*
- structure / tire construction (i.e. radial)
- rim diameter
- load index
- speed rating
- extra load capacity / load range (optional)
Each of these is important, but the markings indicating the size of the tire are particularly useful. On Nokian Tyres' website, you can search for tires suitable for your vehicle based on your tire size. Enter the tire width in millimeters and the height and rim size in inches on the page. You will get suggestions for tires suitable for your car by size.
*Image below highlights the aspect ratio of the tire pictured.
How to check tire condition?
As previously mentioned, it's important to be able to interpret the condition of your tires in other ways than just their age. Even if a tire has several years of lifespan left according to recommendations, the tire may already be too worn out. In addition to the number of years, the tire’s tread depth helps in assessing its condition.
There are separate requirements for the tread depth of all season tires and winter tires. The minimum allowed tread depth for all season tires is 1.6 mm and for winter tires is about 4 mm, depending on the country and the relevant local laws.
Even if the legal requirements are met, it is still advisable to change the tires to new ones sooner rather than later. This is because the grip and driving characteristics of the tires deteriorate in demanding situations as they wear. In the case of studded tires, be sure to pay attention to the tire studs and how many there are left between all four tires in addition to being mindful of tread depth.
The wear of tires is affected by age, mileage and driving style, vehicle overloading as well as tire quality. With high-quality tires, you can drive significantly longer compared to cheap but poor-quality ones. Therefore, choose reliable, premium tires from Nokian Tyres for your car. All Nokian Tyres products have a Driving Safety Indicator (DSI) on the tread surface, which gives information about the remaining tread depth without the need for a depth gauge. The image below shows what our patented DSI looks like on a tire.
