How To Read A Tire Size – A Full Instruction

ByThe Old Racer
Table of contents

When purchasing new tires, users are frequently concerned with the manufacturer and the price. They are less concerned with the parameters of the automobile tires that are appropriate for their needs. As a result, there have been numerous instances involving tire explosions while driving at high speeds or with very noisy tires,… 

This may affect the safety of the vehicle’s operation; consequently, we will provide key tire metrics that users should consider when purchasing tires. All will be here in this post on how to read a tire size.

How To Read A Tire Size?

How To Read A Tire Size

The tire specifications are printed on the tire’s sidewalls and are combined into a long series of numbers. By understanding what each of these letters means, you can be sure you’re using your tires as efficiently as possible.

Suppose in this article; we have a series of symbolic numbers that P185/75R14 82S, so the parameters on the tire wall can be divided as follows:

Specifications Of Tires

  • P – Vehicle type: The tire code’s first letter identifies the vehicle type that can use it. P “Passenger”: tires designed for cars that can transport “passengers.” Other varieties include LT (Light Truck): light trucks, pickup trucks, and T (Temporary): temporary replacement tires. In the above illustration, we can see that this is a popular tire used to transport passengers.
  • 225 – Tire width refers to the tire’s contact surface with the road surface. The breadth of a tire is measured from wall to wall (mm).
  • 70 – The sidewall height to tire surface width ratio, as computed by the tire thickness/width ratio. The preceding example’s thickness is 75% of the tire width (185).
  • R – Tire structure: The most prevalent automobile tire structure is Radial, which corresponds to the letter R. Furthermore, tires with letters such as B, D, or E are exceedingly rare.
  • 16 – Wheel diameter: Only one wheel size can be utilized for each type of tire. The number 14 relates to the 14-inch wheel diameter.
  • 91S – Load and speed limit: If this figure is less than the vehicle’s load and speed, the cause of the tire explosion is unknown.
  • *No.xx – Tire load capacity: Typically, xx position ranges from 75 to 105, corresponding to a load of 380 to 925 kg.

Tire Expiration Date

There is always another 4-digit code on the tire’s side that indicates the manufacture date. If the last four numbers of the sequence are 2118, it signifies that the tire was sent in the 21st week of 2018. 

The manufacturer recommends a maximum shelf life of 6 years from the production date. When the expiration date passes, the tire loses all of its fundamental characteristics. The manufacturer has anticipated this and recommends that even unused tires that have just been stored in storage but have expired are considered to have reached the end of their useful life.

Other Automobile Tire Criteria

The results of government tests for tread wear, traction, and heat resistance are displayed in Uniform Tire Quality Grades. The test, however, is delegated to the manufacturer.

  • Treadwear is a tire tread wear parameter that has a value of 100. You should note that the tire wear resistance rating is only valid for comparing items from the same manufacturer and is not relevant for comparing products from other manufacturers.
  • Traction is a tire’s ability to stop on a straight path on a smooth surface.
    • The highest ranking is AA.
    • A – The very best
    • B – Standard
    • Acceptable ©
  • Temperature measures a tire’s ability to withstand temperature when driving over long distances at high speed, tire tension, or overload.
    • A – The best
    • B – Average
    • C – Acceptable
  • Maximum load: the maximum weight the tire can bear, in pounds or kilograms.
  • Maximum Inflation Pressure: in units of psi (pounds per square inch) or kPA (kilopascal). Never inflate tires beyond the maximum air pressure specification. Otherwise, you will experience side effects such as vibrations or punctures.

FAQs

What Do The Three Numbers Mean On Tire Size?

These are the three digits immediately following the letter indicating the tire classification. This parameter helps us to know the width when in contact with the road surface of the tire. This way, drivers can choose the most suitable size for their part of the road, depending on the terrain conditions.

Can I Use 235 Tires Instead Of 225?

These two numbers represent two different tire sizes with different widths. The 235 mm tire is larger than the 225 mm tire, so it is generally suitable for heavy-duty vehicles. With these vehicles, 225 tires may not be enough to carry. The 225 tire is more popular for small cars, which usually have lighter operating loads.

Do Bigger Tires Give A Smoother Ride?

This is not what you believe, as larger wheels make driving more difficult. Because you will be able to feel the vibration and shock more clearly, manufacturers are working to limit this. Experts continue to advise choosing a wheel with wide, elastic tires. This way, you will minimize the impact of bad terrain on your vehicle.

How Much Difference In Tire Size Is Acceptable?

We recommend that you do not select parameters that deviate significantly from the car handbook. The maximum recommended by specialists is 3%; if you cannot find the proper gadget, you can add 3% to each parameter specified by the manufacturer.

Conclusion

Above is full instruction on how to read a tire size. If you master this information, you can recognize and make smarter decisions to protect your vehicle. This regulation can be applied to all car tires currently on the market. Thank you for taking the time to read this article; I hope you found it useful.

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