All tyres look pretty much the same. The branding, grooves and size might vary, but to the undiscerning eye, they are all just black and round. Yet every tyre is unique and is embossed with its own insignia. Known as DOT codes (an abbreviation for the US Government’s Department of Transportation), they contain a vital piece of information vehicle owners need to be aware of: the age of your tyre. For this reason, the DOT code is widely regarded by many as a birth certificate for your tyre.
Since most motoring and safety groups recommend replacing car and van tyres when they are between seven and 10-years-old and caravan and motorhome tyres five to six year years after they were manufactured, regardless of their condition or how many miles they have done, recognising how old your current tyres are is vitally important.
DOT codes also contains other information, such as where in the world your tyre was manufactured and details about its size.
So how do you identify and decipher the information displayed in your tyres DOT code? Our definitive DOT code guide explains all you need to know.
What does a DOT code look like?
It is easily distinguishable from the other markings on the tyre sidewall, because it begins with the letters DOT. It is then followed by a series of seven to 12 characters grouped into three or four sections.
This is a typical example:
In the first sequence of characters, the first four numbers and/or digits denote the tyre manufacturer, plant code and tyre size. The first two identify the plant in which the tyre was produced. Every tyre manufacturer will have several factory codes referring to various plants around the world. For example the HD denotes a Michelin tyre produced at the Cuneo factory in Italy.
The third and fourth characters are the tyre size code.
The second series of characters, containing 0-4 characters letters and/or digits, is the optional manufacturer’s construction code. This identifies significant characteristics of the tyre, such as pattern.
While neither of these pieces of information are of any great interest to the average tyre purchaser, the last four numbers in the DOT codes sequence are extremely important. They reveal the age of the tyre.
Using the DOT code to decipher the age of your tyre
Before we explain how to decipher this bit of the code, you need to understand why it is important to know the age of your tyres. Tyre are not designed and manufactured to last forever. They are made of rubber, which is perishable. Just like the soles of your shoes wear out, so do your tyres. Furthermore, even if they are not used much, the rubber will deteriorate over time, making them potentially dangerous. For example, tyres not driven on much but regularly exposed to the sun and high temperatures will crack and perish long before the tread wears down to the legal minimum limit of 1.6mm.
The next key fact to remember is that you should not judge the age of your tyre based on how long it has been fitted to your car. Its age is defined by the date it was manufactured. This is where DOT codes come in. Although the manufacture date is coded, you don’t need to be a Mensa member to figure it out. Just follow these steps.
How to decipher DOT codes
Locate the last four characters of the DOT code to determine when your tyre was produced. There is lots of information on the sidewall (as you can see in the TyreSafe diagram on the right). The code is quite small, but easy to spot because it begins with the letters DOT! The first two digits are the week of manufacture, and the last two numbers indicate the year. For example, 0517 means the tyre came of the factory line during the fifth week of the year 2017. It really is that easy.
Tyres that are made from the year 2000 onwards have a four digit code, such as 2013. Alarm bells should start ringing if your DOT code is only three digits! This means your tyre was manufactured before 2000 and is has already exceeded its recommended shelf life. We urge you to replace it immediately.
When are your tyres too old to use?
Just to reiterate, tyres are meant to provide thousands of miles of service. However, they are not indestructible or intended to last for eternity. Which is why experts recommend they are replaced when they are between seven to 10-years-old.
This advice is not a marketing ploy to get you to buy more tyres. It makes sense that the components within a tyre dry out with age and can separate. The process could cause an elastic band to weaken and break. However, with a tyre the consequences are potentially much more catastrophic, leading to tyre failure and deflation.
So if you want to check the age of your tyres, including the spare, especially if your vehicle is more than six years old and you have never replaced them, do it immediately. We have shown you how easy it is. It only takes a couple of minutes. You don’t need to Google anything or rifle through a drawer full of old receipts. Just follow the etyres DOT codes guide.
Denna Bowman, Head Office