How to Read Your Tyre Size
Have you ever looked at the sidewall of your tyre and wondered what all the letters and numbers mean? While it may look like a complicated code, every marking provides important information about your tyre’s size, construction and capabilities.
Understanding these markings makes it easier to choose the correct replacement tyre and ensures it meets your vehicle’s requirements.
Understanding a Tyre Size
A typical tyre size might look like this:
265/60R18 114T M+S
Here’s what each part means:
| Marking | Meaning |
|---|---|
| 265 | Tyre Width – The tyre is 265 millimetres wide from sidewall to sidewall. |
| 60 | Aspect Ratio – The sidewall height is 60% of the tyre’s width. |
| R | Construction – “R” stands for Radial construction, the most common tyre construction used today. |
| 18 | Rim Diameter – Designed to fit an 18-inch wheel. |
| 114 | Load Index – Indicates the maximum load the tyre can safely carry when correctly inflated. |
| T | Speed Rating – Indicates the tyre’s maximum certified speed under specified test conditions. |
| M+S | Mud & Snow – Indicates the tyre is designed to provide additional traction in light mud and snow conditions. |
What is a Dual Load Index?
Some tyres, particularly those designed for light trucks, vans and commercial vehicles, feature a dual load index, such as 121/118.
The two numbers represent different maximum load capacities depending on how the tyre is fitted.
- 121 – Maximum load when the tyre is fitted as a single wheel.
- 118 – Maximum load when the tyre is fitted in a dual-wheel configuration.
Dual-wheel applications are commonly found on commercial vehicles, where two tyres share the load on each side of the axle.
Common Tyre Prefixes and Markings
You may also notice additional letters before or after the tyre size. These indicate the tyre’s intended application.
| Marking | Description |
|---|---|
| P | Passenger vehicle tyre (primarily used in North America). |
| LT | Light Truck tyre, designed for utes, vans and vehicles carrying heavier loads. |
| C | Commercial-rated tyre with increased load capacity, commonly used on vans and light commercial vehicles. |
| T | Temporary spare tyre intended for emergency use only. |
| ST | Special Trailer tyre, engineered specifically for trailer applications. |
| XL | Extra Load tyre capable of carrying greater loads through higher inflation pressures. |
| RF / RFT / Run Flat | Run-flat tyre designed to continue driving for a limited distance after a puncture. |
Why Understanding Tyre Markings Matters
Your tyre’s sidewall contains important information that helps ensure you choose the correct replacement tyre for your vehicle. Selecting the right size, load index and speed rating helps maintain your vehicle’s safety, handling and performance.
