How to Read Tire Size and Manufacture Date

Table Of Contents:

  • Where do you find the tire size and manufacture date?
  • How do you read a tire size? A practical example of 265/65R17
  • What do the load index and speed rating on a tire mean?
  • How do you find the tire manufacture date from the DOT code?
  • What other markings are printed on the tire sidewall?
  • How long does a tire last, and how does summer heat affect it?
  • How do you use this information when buying new tires or a used car?
  • Frequently asked questions about tire size and manufacture date

You read a tire size from the number printed on its sidewall, such as 265/65R17: the first number is the tire width in millimetres, the second is the ratio of the sidewall height to the width, the letter R means the tire has a radial construction, and the last number is the rim diameter in inches. The tire manufacture date is found in the last four digits of the DOT code; the first two digits are the week number and the last two are the year of manufacture, so the code 2324 means the twenty-third week of 2024. In this article we explain the rest of the numbers and symbols printed on tires, and how to use them when replacing tires or buying a car.

Where do you find the tire size and manufacture date?

All the information you need is printed on the tire sidewall, but the original size recommended by the car manufacturer has other sources too:

  • The tire sidewall: the size is shown in clear characters, usually followed by the load index and speed rating.
  • The DOT code: a series of letters and numbers that starts with the word DOT and ends with the manufacture date; the full code may appear on only one side of the tire.
  • The sticker on the driver’s door frame or inside the fuel filler flap on many cars, which shows the original size and the recommended air pressure.
  • The owner’s manual, which lists the approved sizes for the car; there may be more than one size depending on the trim and rim size.
  • The spare tire may be a different size from the main tires on some cars, so do not rely on it to find out the size.

 

How do you read a tire size? A practical example of 265/65R17

  1. 265: the tire width in millimetres from one side to the other; the bigger the number, the wider the tire.
  2. 65: the ratio of the sidewall height to the tire width, meaning the sidewall height equals 65 percent of the width; a smaller number means a shorter sidewall, which is common with large rims.
  3. R: the type of tire construction, meaning it is radial, which is the common construction in car tires today.
  4. 17: the diameter in inches of the rim the tire is fitted on, which must match the rim size exactly.
  5. You may find the letter P before the size, indicating a passenger car tire, or LT, indicating a light truck tire designed for higher loads, or there may be no letter at all.

 

What do the load index and speed rating on a tire mean?

Right after the size you will usually find a number and a letter such as 112T, and these are among the most important things to match when replacing tires:

  • Load index (112 in the example): a number indicating the maximum weight a single tire can carry at the specified pressure, converted to a weight using a standard table; 112 equals 1,120 kilograms per tire.
  • Speed rating (T in the example): a letter indicating the maximum speed the tire is designed to sustain under test conditions; for example, T means 190 km/h, H means 210 km/h, and V means 240 km/h.
  • This rating is not an invitation to drive at that speed; it is a limit of the tire’s capability, and keeping to the posted speed limits on the road is always a must.
  • When buying, choose a load index and speed rating equal to or higher than those recommended by the car manufacturer, and never lower.
  • The XL or Reinforced marking means the tire is reinforced to carry a higher load than a standard tire of the same size, and it may need a different air pressure according to the manufacturer’s recommendation.

 

How do you find the tire manufacture date from the DOT code?

  1. Look on the sidewall for the word DOT followed by a group of letters and numbers representing the factory code and tire specifications.
  2. Look at the last four digits of the code, which are usually inside a small oval frame or set apart from the rest of the code.
  3. The first two digits are the week of the year, and the last two digits are the year of manufacture.
  4. Example: the code 2324 means the tire was made in the twenty-third week of 2024, and the code 0825 means the eighth week of 2025.
  5. If you cannot find the four digits on the outer side, look at the inner side of the tire.
  6. If you find only three digits instead of four, the tire is very old and was made under an earlier coding system, and using it is not advisable.

 

What other markings are printed on the tire sidewall?

  • MAX PRESS: the maximum air pressure the tire can withstand, not the pressure you should inflate it to; the correct pressure is on the driver’s door sticker or in the owner’s manual. To learn about the effect of incorrect pressure, read about the causes, signs, and solutions for low tire pressure.
  • TWI or a small triangle mark on the tire shoulder: it shows where the wear indicators are inside the tread, and when the tread surface wears down to their level, the tire must be replaced.
  • ROTATION with an arrow: it means the tire has a specific direction of rotation and must be fitted so that it turns in the direction of the arrow.
  • OUTSIDE and INSIDE: these appear on asymmetric tires to show which side faces outwards when fitted.
  • TUBELESS: it means the tire works without an inner tube, which is common on modern cars.
  • M+S: it means the tire is designed to handle mud and snow to some degree, and you often find it on four-wheel-drive vehicle tires.
  • Some tires carry ratings for treadwear, traction, and temperature resistance (Treadwear, Traction, and Temperature) that help you compare tires.

 

How long does a tire last, and how does summer heat affect it?

  • Rubber ages over time even if the tire is not used much, so tread depth alone is not enough to judge whether a tire is still fit for use.
  • High heat and direct sunlight speed up the hardening and cracking of rubber, which matters in the Kingdom’s hot climate, especially for cars that stand in the sun for long periods.
  • There is no single lifespan that suits every tire; some tire and car manufacturers recommend regular inspection after several years from the manufacture date and replacement after a set period regardless of tread condition, so refer to the owner’s manual and the tire maker’s recommendations.
  • Signs of an ageing tire include fine cracks in the sidewall or between the tread blocks, hardened rubber, and a change in its colour.
  • Any bulge or bubble on the side of a tire is a danger sign that requires replacing it immediately and not travelling on it.
  • The spare tire ages too, so check its date and pressure from time to time even if you have never used it.

 

How do you use this information when buying new tires or a used car?

  1. Stick to the size recommended for your car, and if you want to change the rim or tire size, consult a specialist, because changing the overall wheel diameter can affect the speedometer reading and safety systems; to learn about the effect on fuel consumption, read about how the wrong rims affect fuel consumption.
  2. Read the manufacture date on every tire before fitting, ask for it to be as recent as possible, and make sure the tires have similar manufacture dates.
  3. Fit two tires of the same size, type, and wear level on each axle, so the car does not behave differently when braking or cornering.
  4. When inspecting a used car, read the dates on all four tires and the spare; old tires or tires of different sizes and types mean an expense coming your way soon, and this is one of the important tips before buying a used car.
  5. Look at the wear pattern too; one edge wearing more than the other may point to a problem with wheel alignment or the suspension.
  6. After fitting new tires, ask for them to be balanced, and set the air pressure according to the driver’s door sticker, not the number printed on the tire.

 

Frequently asked questions about tire size and manufacture date

  1. Can I fit a tire with a different size from the original? The car manufacturer may approve more than one size, but any change outside the approved sizes should be made after consulting a specialist, because it can affect steering, the speedometer, and braking.
  2. Is an unused tire new regardless of its date? No; rubber also ages in storage, so ask for a recent manufacture date and make sure it was stored away from sun and heat.
  3. What is the difference between 265/65R17 and 265/70R17? The width and rim diameter are the same, but the sidewall of the second is taller, so the overall wheel diameter is larger, and swapping between them is not advisable without checking the car’s specifications.
  4. Is good tread depth enough? No; also check the manufacture date and the condition of the sidewall, because an old tire may have hardened, cracked rubber even though its tread looks good.
  5. Where do I find the right air pressure for my tires? On the sticker on the driver’s door frame or in the owner’s manual, not the number printed on the tire sidewall.

 

Reading the numbers printed on the sidewall takes no more than a minute, but it protects you from buying the wrong size or a tire that has been sitting in storage for a long time. Remember three rules: the size must match the car manufacturer’s recommendation, the last four digits of the DOT code tell you the tire’s age, and the correct pressure is written on the driver’s door, not on the sidewall.

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