Understanding Tire Maintenance Description: Speed ​​Rating and Load Index

There never seems to be a shortage of questions you get asked when you ask about tires. What size do you need? What speed rating do you need? How will you use them? What load index do you need?

Where do you find this information and what does it even mean? It may seem overwhelming, but knowing a few key points will help you find the right tire for your vehicle.

Where to Find the Load Index and Speed ​​Rating on Your Tire

Your tire size is marked on the sidewall of your tire in the format 215/60R16. Immediately following the tire size is another number and a letter like 94S. This is the load index and speed rating of your tire. Let's decipher it.

Load index

The number is load index. It shows how much weight the tire can support. The higher the load index, the more weight it can carry:

Load Index Chart Example

As you can see, the number 94 means that each tire can carry up to 1,477 pounds of weight or 670 kg. The load index of your tires must not be lowered. The tire fits the vehicle exactly when it is designed. Using a tire with a lower load index may result in unwanted wear or tire failure. You can use a higher load index than your vehicle was originally equipped with and the load capacity will increase.

Speed ​​rating

Next to the load index is a letter indicating the speed rating. In our example, this is the letter S. As with the load index, the higher the letter in the alphabet, the higher the speed rating:

Speed ​​Rating Chart Example

The speed rating is the maximum speed the tire can be driven to. A tire's speed rating will be voided if it has been punctured, patched or otherwise damaged. The manufacturer can no longer guarantee the safe operation of the tire at high speeds.

High Performance Rating

Performance tires have speed ratings a little differently. In a tire size, the addition of the letter Z indicates that it is a tire capable of speeds in excess of 149 mph. Displayed as: 215/60ZR16

This was thought to be as much as needed, and the Z rating covered all tires rated at 149 mph and above. Since the introduction of Z-rated tires, further refinements have taken place that have defined specific speed ratings for speeds above 149 mph. W-rated tires mean tires are capable of speeds up to 168 mph, while tires rated Y are capable of 186 mph. Anything beyond the Y index is indicated by the load/speed index in brackets. For example, this might be shown as (99Y).