When it comes to maintaining your vehicle, understanding the specifications of your tyres is crucial. Tyre sizes might seem like a string of numbers and letters, but they convey essential information about the tire’s dimensions, capabilities, and compatibility with your vehicle. In this blog, we’ll unravel the mystery behind tyre sizes, breaking down the alphanumeric code to empower you with the knowledge needed to make informed decisions about your vehicle’s rubber companions.

Breaking Down the Tyre Size Code:

Tyre sizes are typically represented by an alphanumeric code, such as P215/60R16. Let’s break down each component:

  1. P (or No Letter): This indicates the type of tyre. “P” stands for Passenger, while the absence of a letter might mean the tyre is for Light Truck (LT) use.

  2. 215: This number represents the tyre’s width in millimeters, measuring from sidewall to sidewall when mounted and inflated but not under load.

  3. 60: This number is the aspect ratio, expressing the tyre’s profile height as a percentage of its width. In this case, the height is 60% of the tyre’s width.

  4. R: This letter denotes the construction type, with “R” indicating radial construction, the most common type for modern vehicles.

  5. 16: This number is the diameter of the wheel, measured in inches. In this example, the tyre is designed to fit a 16-inch wheel.

Understanding Load Index and Speed Rating:

Apart from the alphanumeric code, tyres also feature two more specifications: the load index and speed rating.

  1. Load Index: This numerical code represents the maximum load-carrying capacity of the tyre. The higher the load index, the greater the load-carrying capacity.

  2. Speed Rating: This letter indicates the maximum speed the tyre can sustain safely. For instance, “H” might indicate a maximum speed of 130 mph. It’s essential to match the speed rating to your vehicle’s capabilities.

Choosing the Right Tyre Size:

Selecting the right tyre size is crucial for optimal vehicle performance, safety, and fuel efficiency. Consult your vehicle’s manual or the placard on the driver’s side door jamb for the manufacturer’s recommended tyre size. Deviating from these specifications can affect handling, traction, and overall safety.

Upgrading or Plus-Sizing:

Some enthusiasts opt for plus-sizing, which involves fitting larger diameter wheels and lower-profile tyres to enhance performance and aesthetics. While this can be done, it’s vital to maintain the overall diameter to prevent speedometer inaccuracies and interference with the vehicle’s suspension.


Understanding tyre sizes is key to maintaining a safe and efficient driving experience. The alphanumeric code, load index, and speed rating all provide valuable information about your tyres. By decoding these specifications and adhering to your vehicle manufacturer’s recommendations, you can confidently navigate the world of tyres, ensuring that your vehicle rolls smoothly, efficiently, and safely down the road.

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Explained How Tyre Sizes Work