A label in plain sight
Every tire carries molded markings on its sidewall that describe what it is, what it can carry and when it was made. They look cryptic, but they follow a standard format that is easy to learn. This article uses a hypothetical example to show how to read each part. Always match any replacement to the sizes recommended by your vehicle’s maker, not just to what is on the tire currently fitted, since a previous owner may have changed it.
The size code
A typical passenger tire reads something like this:
205/55R16 91V
Reading from left to right:
- 205 is the section width, in millimeters, measured from sidewall to sidewall.
- 55 is the aspect ratio. It means the sidewall height is 55 percent of the width. Here, 205 x 0.55 comes to about 113 millimeters.
- R means radial construction, which is nearly universal on passenger cars.
- 16 is the diameter of the wheel rim in inches. The tire must match the wheel exactly.
- 91 is the load index.
- V is the speed rating.
Some tires start with a letter, such as P for passenger or LT for light truck. This indicates the intended use and may affect load calculations. Some size codes include an additional letter such as R for radial or ZR on some higher-speed tires; the details can differ by market.
Load index
The load index is a number that corresponds to the maximum weight one tire can carry when properly inflated. It is a code, not the weight itself. A load index of 91, for instance, corresponds to about 615 kilograms per tire (about 1,356 pounds). A chart gives the figure for any index. A replacement should have a load index at least as high as the one your vehicle’s maker specifies. Using a lower index is unsafe.
Speed rating
The speed rating is a letter showing the highest sustained speed the tire was tested for under its rated load. Common letters include:
- S: about 112 mph (180 km/h)
- T: about 118 mph (190 km/h)
- H: about 130 mph (210 km/h)
- V: about 149 mph (240 km/h)
The rating does not mean you should drive at those speeds or that the tire is safe at them in any condition, and speed limits still apply. Like the load index, it is a minimum to meet. Different ratings can also affect ride and handling, and mixing very different ratings on one car is usually discouraged. Check your manual or a tire technician.
The DOT code and date of manufacture
In the United States and some other places, a sequence beginning with the letters DOT is molded on the sidewall. It identifies the plant and tire, and the last four digits give the date of manufacture. The first two of those digits are the week of the year, and the last two are the year.
As a hypothetical example, a code ending in 2321 would mean the 23rd week of 2021. Tires made before the year 2000 used a three-digit format, which is a sign of a very old tire.
The date is useful because rubber ages even when the tire is unused. A tire in storage or a spare that has never touched the road can still be old. Age limits and what to do about them are covered in the article on when to replace tires based on tread depth and age.
The date code is sometimes only printed on one sidewall. If you cannot find it on the outer side, check the inner side.
Other markings you may see
- M+S or M&S: mud and snow. This is a marking about tread design and does not guarantee winter performance. The differences between seasonal types are covered in the comparison of summer, all-season and winter tires.
- Three-peak mountain and snowflake symbol: a symbol indicating the tire met a defined snow-traction test in regions that use it.
- UTQG ratings: used in the U.S., with a treadwear number, a traction grade (AA, A, B or C) and a temperature grade (A, B or C). The treadwear number is a comparison value from the manufacturer’s testing, and not a mileage promise.
- Maximum pressure: a figure for the tire’s limit. It is not the recommended pressure for your car, which is found on the vehicle label, as described in the guide to checking tire pressure.
- Tread wear indicators: small arrows or marks that point to raised bars in the grooves.
- Direction arrows: marked “rotation” with an arrow on directional tires, which must be mounted to roll the right way.
- Inside and outside: some asymmetric tires are marked to show which side faces out.
- Run-flat markings: various manufacturer symbols or letters denote a run-flat design, which is explained in the article on run-flat tires.
- Reinforced or XL: the tire is built for higher pressure and load.
Putting it together
When buying or comparing tires, check four things in order: the size, the load index, the speed rating and the age. Make sure they meet or exceed your vehicle’s requirements. Beyond that, the seasonal type and tread design are choices about how you drive and where.
If anything on a tire seems inconsistent, unreadable or does not match your vehicle’s label, a tire shop can help. Markings and rules vary somewhat between regions, so check what applies where you live.