How To Read Tire Codes & When Do You Need To Change Your Car Tires

How To Read Tire Codes & When Do You Need To Change Your Car Tires

Reading Ronald Montoya’s post at and Jason Fogelson’s post at concerning car tires, we can conclusively draw a summary from both posts on what you need to know about tires.

10 Tips When Buying A New Tire

According to Jason, there are 10 great tips to be followed when buying new tires which he highlighted as;

  1. Make sure you need a new tire: This has to do with the duration of the previous tire and signs that show it has gone bad, such as worn surfaces.
  2. Make sure that your car is in good shape: Before changing the tire of your car, ensure the car is in good condition because tires deteriorate over time whether they were put to use or not.
  3. Check your owner’s manual and information placard: it is not enough to make the decision of buying the tire but the type and size also matter, going through the car manual to obtain all the specifications is necessary.
  4. Understand the decipher tire code: according to Jason here is what he said about decipher codes: “Example of tire sidewall markings — P215/65R 15 95H M+S
  • First up is a letter or letters, indicating the tire’s purpose: “P” for passenger cars or “LT” for light trucks are the most likely letters you’ll see.
  • Next is a three-digit number. This is the tire’s width (in millimeters) from sidewall edge to sidewall edge.
  • Then, a two-digit number which is the tire’s aspect ratio, or the ratio of height to width. The smaller the number, the shorter the sidewall.
  • Next, a letter, probably “R,” which indicates radial construction. Almost every tire you encounter will be a radial nowadays unless you’re buying tires for a classic car.
  • Then, another two-digit number, which is the diameter of the wheel that the tire is intended to fit.
  • Next, an optional two- or three-digit number. This is the tire’s load index number, and its inclusion is not required by law. The load index number corresponds to the tire’s load-carrying capacity. A site for discount tires has posted a handy chart with the load index numbers and loads. Simply put, don’t install a tire with a lower load index number than your manufacturer recommends. AOL Autos: Tire shopping lessons
  • Next, a letter. This is the tire’s speed rating. Follow your manufacturer’s recommendation. You should only need to upgrade to a higher speed rating if you have modified your vehicle for track use, or if you are heading to Germany to drive on the Autobahn.
  • Next, some more letters, usually “M+S” or “M/S.” This stands for mud and snow, and applies to most radial tires sold in America.”
How To Read Tire Codes & When Do You Need To Change Your Car Tires
How To Read Tire Codes & When Do You Need To Change Your Car Tires

  1. Consider the wheels: the size of the wheel must match with any tire you are intending to buy.
  2. Buy a full matching set: sometimes, it is necessary to buy the full matching sets of the tire instead of buying in pieces.
  3. Check on your spare: you don’t need to buy tires only when the cars have started having worn surfaces, you can regularly check on them and the spare tire for a replacement ahead of time.
  4. Consider buying over the internet or catalog: to trust the specifications of the tire and to be able to deal directly with the specialists, consider making your tires as an order from either internet or manufacturers’ catalog.
  5. Break in your new tires carefully: new tires can get damaged quickly not actually that they have expired but because of wrong handling of it, so look for a professional that will assist you in removing your old tire and fixing the new one without any damage.
  6. Maintaining your new tires: maintaining the new tire involves constant monitoring of the tire and avoiding reckless driving, check for all the specifications that came with the new tire and ensure you do not exceed the limits, like the load limit, speed, and age limit.

Having said all that, let us read what Ronald said in his own post about tires.

According to his post, an owner of a 1998 Ford Explorer bought a used tire which was about 10 years old, thinking it was a new one not until the tread of the tire suddenly separated from it two weeks later while on a speed.

The incident led to the total loss of control of the vehicle which hit a motorcycle and killing its rider. Such a bad story though, but that is what ignorance could cost.

That a new vehicle was packed for 7 years does not mean it is safe to drive it without changing the tires.

Though a tire may appear good visually but if the tire had been manufactured ten years earlier, then there is need to change it irrespective of how strong it may appear.

The reason for this was according to the Sean Kane’s comparison of tires to rubbers, he is the President of Safety Research & Strategic Inc.,

“If you take a rubber band that’s been sitting around a long time and stretch it, you will start to see cracks in the rubber,” says Kane, whose organization is involved in research, analysis, and advocacy on safety matters for the public and clients including attorneys, engineering firms, supplier companies, media and government. That was Kane’s comparison of tires to rubber.

The major problem some people have is how to differentiate used tires from new ones in the market due to the tricks involved in the business.

Though there are reasons many tire dealers recycle the used tires whose appearance are still good and that is because some of them or the local dealers among them believed that only the tires with worn surface shouldn’t be recycled while others can be recycled to the buyers hence there appearance is still good.

Let us reveal a little trick on how to know the specifications of tires and the way of understanding the codes.


Going through Ronald’s post, here is what he revealed about knowing the age of your tire.

How To Read Tire Codes & When Do You Need To Change Your Car Tires
How To Read Tire Codes & When Do You Need To Change Your Car Tires

“Tires made after 2000 have a four-digit DOT code. The first two numbers represent the week in which the tire was made.

The second two represent the year. A tire with a DOT code of 1109 was made in the 11th week of 2009. Tires with a three-digit code were made prior to 2000 and are trickier to decode.

The first two digits still tell you the week, but the third digit tells you the year in the decade that it was created.

The hard part is knowing what decade that was. Some tires made in the 1990s (but not all) have a triangle after the DOT code, denoting that decade. But for tires without that, a code of “328” could be from the 32nd week of 1988 — or 1978.”

Having said summarized this post this way according to my research, you are free to ask any question in regard to any area that might seem confusing to you.

Philip Nduka

Philip is a graduate of Mechanical engineering and an NDT inspector with vast practical knowledge in other engineering fields, and software.

He loves to write and share information relating to engineering and technology fields, science and environmental issues, and Technical posts. His posts are based on personal ideas, researched knowledge, and discovery, from engineering, science & investment fields, etc.

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