The markings on a tyre sidewall tell you its size, load capacity, speed rating, and when and where it was made. Learning to read them helps you check that a replacement is suitable and that a used or stored tyre is still fresh. This guide explains the main markings, how the DOT code works, and what to check before buying.
Reading the tyre size
A typical size reads something like 225/45R17. The first number is the width in millimetres, the second is the aspect ratio (the height of the sidewall as a percentage of the width), the letter R means radial construction, and the last number is the wheel diameter in inches. Any replacement must match these, or be an approved alternative.
Load index and speed rating
The load index is a number that shows the maximum weight each tyre can carry. The speed rating is a letter that shows the maximum speed the tyre is rated for. Both must meet or exceed the requirement for your vehicle, and the figures are given in the owner’s manual.
The DOT code
Every tyre sold for road use in the US has a DOT code on its sidewall. It begins with the letters DOT and identifies the manufacturer, the plant, and the tyre type. The final four digits show the week and year of manufacture. For example, 2419 means the 24th week of 2019. Tyres made before 2000 have a three-digit date code.
Why the date matters
Rubber ages even when unused, and many manufacturers advise replacing tyres after a set number of years, often around six to ten years from manufacture, regardless of tread depth. Check the date code before buying, especially for stored or discounted stock.
Other markings to look for
Look for the three-peak mountain and snowflake symbol if you need winter performance, and check the load range markings on trailer and heavy-duty tyres. Tread wear indicators and the maximum pressure are also marked on the sidewall.
Checking tyres before you buy or fit
Confirm the size, load and speed ratings, and the DOT date code. Inspect the sidewall for cracks, bulges, and cuts. Check that the tyre is approved for the wheel width, and ask a fitter to confirm the match before fitting.
Frequently asked questions
Where is the tyre manufacturer code? The DOT code is on the sidewall, usually near the rim. It identifies the manufacturer and plant.
Does the sidewall show the maximum pressure? Yes, but the recommended pressure for your vehicle is in the owner’s manual or on the door placard, and that is the figure to use.
Can I read the tyre age from the size marking? No. The age comes only from the DOT date code.
Get help reading your tyres
For more on choosing and caring for tyres, read our tire guides. If you are not sure what the markings on your tyres mean, contact us and we will help you read them.