How to Read Tire Sizes: What 205/55R16 91V Means and How to Read the Manufacture Date

Reading "205/55R16 91V" from the left

The sidewall of a passenger car tire always has a marking like "205/55R16 91V." This is a common international format set by JIS and ISO, so it reads the same whatever the manufacturer. From the left come three numbers giving the tire's size, then information on construction, load and speed.

Only the first part, "205/55R16," relates to size. When buying tires or looking for winter tires, just give this part accurately and a shop can find you tires of the same size. The latter part, "91V," is a guide to choosing performance equal to or above the original equipment.

Other markings: P, LT, ZR, XL and more

On imported cars, SUVs and sports tires, symbols may appear before or after the basic marking. Without knowing their meaning, they can look like a different size, so it's worth knowing the common ones.

• P (e.g. P215/60R16 94H): a passenger car tire under the US P-metric standard. Size reads the same way
• LT (e.g. LT215/70R16 100/97Q): for light trucks. The two LIs are for single use and dual use (double rear wheels)
• ZR (e.g. 245/40ZR19): an older marking for construction rated above 240 km/h. Now written alongside a speed rating, as in "245/40ZR19 (98Y)"
• RF, RFT, ROF and others: run-flat tires (can be driven for a while after a puncture). The symbol varies by manufacturer
• XL, EXTRA LOAD, REINFORCED: extra load standard. Tires with greater load capacity through higher air pressure
• M+S: mud and snow. It means a tread designed with mud and snow in mind, not the same performance as winter studless tires

Paste the marking into the tool's sidewall field, symbols included, in full-width or half-width characters, and it separates out and shows the size, LI, speed rating and XL.

Chart of load index and speed ratings

The load index (LI) expresses as a number the maximum weight one tire can support at a set air pressure. Each step up adds about 2–3%. Common passenger car LIs and their weights are as follows.

When replacing tires, the rule is to choose an LI equal to or above the original equipment. With a lower LI, the tires may not support the car's weight properly and it may fail Japan's vehicle inspection (shaken). You won't reach the top speed on Japanese roads, but higher-rated tires are designed with high-speed stability in mind, so choosing at least the original rating is the safe option. Winter studless tires are an exception, and lower ratings such as Q are common.

Read the manufacture week and year from the four digits in an oval

The tire's sidewall has four digits enclosed in an oval (or rectangle). This is the manufacture date: the first two digits are the week of the year, and the last two are the last two digits of the year. The digits are often stamped on one side only, so they may be hidden on the inner side while the tire is on the car.

A marking with only three digits means the tire was made before 2000 (the first two digits are the week, and the last digit is the last digit of the year). If one is still fitted, it's well past the time to think about replacing it, however much tread remains.

The Japan Automobile Tyre Manufacturers Association (JATMA) recommends an annual inspection for tires that have been in use for 5 years or more, and replacing tires 10 years after manufacture even if tread remains. Before using secondhand tires or winter tires you've been given, check the manufacture date along with the tread depth. Rubber hardens even without use, so even a stored, nearly new tire keeps aging.

Where to check your car's tire size

1. 1

   Look at the sidewall of your current tire

   The most reliable source is the marking on the tire now fitted. Some cars have different sizes front and rear, so check both.

2. 2

   Look at the label inside the driver's door

   A label on the driver's door opening (pillar) shows the original tire size and specified air pressure. Even if a previous owner changed the size, this shows the original values.

3. 3

   Look at the vehicle registration and owner's manual

   The specifications in the owner's manual list the original tire size for each trim. Many cars have different rim sizes by trim, so look at the row for yours.

4. 4

   Enter it in the tool to check the outer diameter

   Enter the size into the Tire Size Diameter Calculator to see the outer diameter, circumference and revolutions per km, and compare the difference with another size.

If your current tire and the door label differ, a previous owner may have fitted plus sizes. When buying winter tires, decide first whether to return to the label's original size or match your current size, so you won't be unsure which wheels to choose. Whether a size change affects the speedometer or vehicle inspection is covered in Speedometer Error from Tire Changes and Inspection Standards.

FAQ

What does "205/55R16" on a tire mean?

205 is the section width (205 mm), 55 is the aspect ratio (sidewall height is 55% of the width), R means radial construction, and 16 is the rim diameter of the matching wheel (16 inches). These three numbers set the tire's size.

What do the 91 and V in "91V" mean?

91 is the load index (LI), meaning one tire can support up to 615 kg. V is the speed rating, meaning it's rated up to a maximum of 240 km/h. When replacing, the rule is to choose both equal to or above the original.

How do I find a tire's manufacture year?

Look at the four digits in an oval on the sidewall. The first two are the week and the last two are the last two digits of the year, so "2523" means week 25 of 2023 (the week of June 19).

After how many years should tires be replaced?

Even with enough tread depth, JATMA recommends replacing tires 10 years after manufacture. After 5 years of use, it's reassuring to have cracks and hardness inspected annually.

What's different about tires marked XL?

XL is the extra load standard: tires that support a greater load at the same size by using higher air pressure than standard tires. At the same pressure as the original tires, they may not deliver their full load capacity, so set the pressure from the tire manufacturer's table.