Comprehensive Guide to Tyre Load Rating and Tyre Speed Rating

Understanding tyre load and speed ratings is essential for ensuring the safety, efficiency, and performance of any vehicle. Selecting the correct tyres based on these ratings impacts not only the handling of the car but also its ability to carry specific weights and maintain stability at higher speeds. Below, we delve deeply into tyre load rating and tyre speed rating, breaking down their importance and how to decipher them.

Where can you find your tyre's load rating & speed index?

Tyre Placard 

The tyre placard in your vehicle, typically found on the driver's side door frame, inside the glove compartment, or under the bonnet, provides essential tyre specifications. It lists critical information such as the recommended tyre size, load capacity, speed rating, and the correct inflation pressure to ensure optimal performance and safety for your tyres.

Owner's Manual

Your vehicle's owner's manual contains detailed information about the load and speed ratings that comply with Australian standards, often presented in a tyre rating chart. For additional confirmation, you can also reach out to the vehicle manufacturer or verify the details online—just ensure that the source is accurate and reliable.

How to Read the Tyre Sidewall

The tyre's sidewall contains a series of alphanumeric characters, which include details about its dimensions, load rating, and speed index. Here's how to interpret these numbers and letters:

For example, a tyre with the following code: 225/45 R17 94V can be broken down as follows:

• 225: The width of the tyre in millimetres.
• 45: The aspect ratio, which represents the height of the tyre’s sidewall as a percentage of the width.
• R: Stands for Radial construction, the most common type of tyre construction.
• 17: The diameter of the wheel rim in inches.
• 94: The load index, which indicates the maximum load the tyre can carry.
• V: The speed index, which indicates the maximum speed the tyre can handle when operating at its load limit.

Understanding how to read tyre load ratings and speed indexes is essential for ensuring that your vehicle is equipped with the proper tyres for safety and performance. These details are clearly marked on the sidewall of every tyre, providing crucial information about the tyre's capabilities.

What Are Tyre Load Ratings?

Defining Tyre Load Rating

The tyre load rating refers to the maximum amount of weight a tyre can safely support. This rating is critical for maintaining the vehicle's integrity and performance, as using tyres that are not suitable for the weight of the vehicle can lead to severe safety hazards.

Tyre load ratings are expressed as numerical values found on the tyre’s sidewall, which correlate to a specific weight capacity in kilograms. The higher the number, the greater the load the tyre can support.

Tyre Load Index Chart

What Are Tyre Speed Ratings?

Defining Tyre Speed Rating

The tyre speed rating indicates the maximum speed at which a tyre can operate under its specified load capacity. This rating is denoted by a letter, which corresponds to a specific speed. It ensures that the tyres can handle the stress of driving at higher speeds without compromising performance or safety.

Tyre Speed Rating Chart

How Load and Speed Ratings Work Together

It is vital to balance both load and speed ratings to ensure a vehicle’s safety and performance. A tyre that has a high-speed rating but an inadequate load index may perform poorly under a heavy load, leading to potential tyre failure. Likewise, a high load index without the appropriate speed rating could result in handling instability at higher speeds.