The numbers on the side of a tire look like a secret code, but they tell you the size, the load it can carry, the speed it's made for, and even how old it is. Once you can read them, buying the right tire is much easier.
Reading the size
Take a tire marked 205/55 R16 91V:
- 205 is the width of the tire in millimetres.
- 55 is the height of the side wall as a percentage of the width.
- R means radial construction, which is standard on most cars.
- 16 is the wheel (rim) diameter in inches.
- 91 is the load index, a code for how much weight the tire can carry. You can look it up in a chart.
- V is the speed rating, the top speed the tire is designed for.
How old is your tire?
Look for the letters DOT, followed by a code. The last four digits show when the tire was made: the first two are the week and the last two are the year. For example, 2423 means week 24 of 2023. Rubber ages even when a tire isn't used much, so an old tire with plenty of tread can still be unsafe. Many tire makers suggest having older tires inspected regularly and replacing them after about ten years, whatever the tread looks like. Check your manual and ask your tire shop.
Other marks you may see
M+S or a mountain with a snowflake means the tire is made for winter conditions. XL or "reinforced" means a higher load rating. Electric cars sometimes need tires with special markings, so follow the manual.
Buying the right tire
Use the size shown on the sticker in the door frame or in your owner's manual, not just whatever is on the car now, because a previous owner may have changed it. Keep the same size, load index and speed rating unless your manual allows something else. And don't mix very different tires on the same axle.
Also, the pressure to use is on the door sticker or in the manual. The number on the sidewall is only the maximum.
General information only. Check your owner's manual, and ask a qualified mechanic if you're not sure.
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