Knowing what kind of tires fit your car is a key step in buying new tires. One of the most crucial factors to look for when shopping for new tires is their size. Luckily, tire manufacturers have included valuable information about tires and tire sizes that help you choose the right ones. If selecting the right tires proves challenging, you can always turn to your local Nokian Tyres dealer for assistance.
Where is the tire size marking located
Before determining the right tire size, let’s look at where you can find this information on your vehicle. You can identify the correct tire size by checking the size of your old tires, or by referring to your vehicle’s owner’s manual. If you check your old tires, the size marking is indicated on the tire’s sidewall with a code of letters and numbers that can indicate tire width, rim diameter, speed rating and more (205/55 R16).
You can also check the vehicle’s manual, where the car manufacturer has included recommendations for tire size. This information may also be found on a sticker on the driver-side door, or in the hatch of the gas tank.
But what does the information on tire sidewall markings mean for choosing the right tire size?
What information is written on the tire sidewall
The information indicated on the tire sidewall or user manual may seem confusing at first for the uninitiated. Here’s how to interpret tire size from the marking with each piece of information from left to right:
- Tire type
- Tire width
- Aspect ratio (pictured below)
- Tire construction
- Rim diameter
- Load index
- Speed rating
Tire width
The first number you should consider when finding the correct tire size for your vehicle indicates the width of a tire. These three numbers tell you how wide the tire is in millimeters when measured from one sidewall to another. For example, the tire marking “205” means that the tire is 205 millimeters or 20.5 centimeters wide. This translates to ~8.1 inches.
Aspect ratio
Next up in the tire markings, following a slash mark after the tire width number, we have the tire’s aspect ratio. The width of a tire is indicated in millimeters, whereas the aspect ratio is a percentage that tells you the tire’s height divided by its width. A larger aspect ratio translates to a higher sidewall. For example, the aspect ratio of 65% means that the height of a tire is 65% of its width.
Rim diameter
The third number to know when reading tire size is the rim diameter. This one comes after the marking indicating tire construction (most likely, this is the letter R, standing for radial tires). This measurement uses yet again a different unit, as the rim diameter is indicated in inches. Make sure that the diameter of your rims is compatible with the tires you plan to purchase. Otherwise, you may need to upgrade your rims as well.
Load index
A tire’s load index tells how much weight a single tire can support. However, as the name suggests, this is an index, not the amount of weight in kilograms or pounds that the tire can withstand. You need to check a load index table to find the corresponding amount of weight.
Speed rating
The speed rating indicates the maximum continuous driving speed capability of the tire. Which speed rating you should select for your vehicle depends on the make and model of your car. Using tires with a speed rating that is too low can impair driving performance, while too high speed ratings may reduce driving comfort.
What is UTQG (Uniform Tire Quality Grading)
In addition to the size, type, construction, speed rating and load index of new tires, there’s other valuable information that can help you on your hunt for the perfect car tire. The Uniform Tire Quality Grading, or UTQG for short, tells you about the treadwear, traction and temperature grades for all season tires. Just like indicators of tire size, you can find the UTQG markings on the tire’s sidewall. Note that the UTQG markings are used on tires manufactured for sale in the United States.
When comparing Treadwear values between tires, tires from the same manufacturer can be compared. However, different manufacturers may interpret the values differently, and thus comparing UTQG of different tire brands may not be an accurate comparison.
UTQG is a comparison of tires from the SAME MANUFACTURER. Here’s what the different grades in the UTQG system can tell you:
- Treadwear = This number tells you how many miles the tire can be expected to last in use. The grade of 200 means that the tire lasts twice as long as a tire with a grade of 100*. Remember that in real use, a variety of factors affect the ultimate lifetime of a tire.
- *NOTE: When comparing Treadwear values between tires, tires from the same manufacturer can be comparable, however different manufacturers might interpret the values differently and may not be an accurate comparison.
- Traction = The traction grade of a tire is indicated with the letters AA, A, B and C, with AA tire providing the greatest traction on a wet road and C having the least traction.
- Temperature = As its name suggests, the temperature grade of the UTQG system tells you how well the tire withstands heat, the best grade being A.
When to buy new tires
Now you have important information you need to get new tires for your vehicle. Make sure to check the tread depth of your car tires regularly to ensure they’re still ready for the roads. Read more about tread depth and check the safety of your tires. When checking your tires, be vigilent for visible cracks and other signs of damage, as those are indicators that it’s time to replace your tires.
Check the tire sidewall for the DOT code, where you can also find the tire’s manufacture date. Usually, tire lifespan is 6 years in service or 10 years from date of manufacture, whichever comes first. Remember that the service life of your tires depends on how much you drive, the driving conditions and how well the tires have been taken care of.
If you are unsure whether your current tires need an upgrade, you can visit your local Nokian Tyres dealer and ask a professional for help choosing the most suitable tire for your vehicle:
