Load index and speed rating of a tyre are mentioned on the sidewall of the tyre. It is important you know exactly what they are so that you can drive safely. Let’s learn more about them.
What is Load Index?
The Load Index of a tyre is a numerical code written on each tyre. It denotes the maximum weight that each tyre of your vehicle can carry at the maximum speed given by the manufacturer. It is generally a two- or three-digit number which represents the load-bearing limit of each tyre.
How is Load Index Denoted?
Suppose you see 99W written on the tyre.
In this, the first two digits 99 represent the tyre’s load index and the letter W denotes the speed rating of the tyre. Since 99 is the load index, it means that it can carry a weight of 775 kilograms.
It is mandatory for the load index to be mentioned on all tyres manufactured since 1991, except for Z-tyres. The load index rating can be found mentioned on the sidewall of your tyre between the diameter reading and the speed rating.
More About Load Index
You must buy all the tyres of the same load capacity to distribute equal weight on all four tyres of your vehicle. You can even refer to the vehicle owner’s manual to determine the load index of your tyres. Typically, the load indexes of the tyres of passenger cars and light trucks range from 70 to 110.
Load Index Table
|Load Index||Load in Kg per Tyre||Load Index||Load in Kg per Tyre||Load Index||Load in Kg per Tyre||Load Index||Load in Kg per Tyre||Load Index||Load in Kg per Tyre||Load Index||Load in Kg per Tyre|
Speed Rating of a Tyre
The speed rating of a tyre indicates the maximum speed at which the tyre can be driven safely under its approved load capacity. You must use tyres with the right speed rating without which you would be putting lives at risk.
At high speeds, the wheels turn faster which generates more heat. If you do not use tyres that can cope with the extra heat, the tyres may get damaged, or worse, burst.
The load index and speed rating together make the service description of the tyre. It is recommended that you know the service description of your tyres whenever you replace the original equipment tyres. You must match or improve the speed rating and load index of your factory tyres even if you don’t plan on pushing the limits. This will help keep your vehicle’s performance consistent.
We saw earlier that except for Z-tyres, all other tyres must have a load index and speed rating mentioned on the tyres. So, what are these Z-tyres?
Z-tyres represent the tyre speed rating with speeds that exceed 240 kmph. These are usually found on exotic sports cars.
After the Z-tyres were created, even higher speed rating tyres were manufactured with speed ratings of W, Y and (Y). W denotes the speed of 270 kmph, Y is 300 kmph and (Y) is more than 300 kmph.
How to Find Load Index and Speed Rating
If you are unable to read the service description on the sidewall of the tyre, just look at the owner’s manual. It will have the tyre load index and tyre speed rating mentioned in it. You can even ask a tyre professional for help.
Few Important Things to Know
- If your tyres carry more weight than its load index, there will be additional stress on your tyres and other vehicle components. It may also lead to increased fuel consumption, poor vehicle handling and even cause tyre failure like cracking or blowout.
- You can use tyres with a higher load index than that recommended by the manufacturer, but do not use a tyre with a lower load index. A tyre with a lower load index cannot support the weight of the vehicle and its load.
- The same applies when it comes to fitting a tyre with a lower or higher speed. You can fit new tyres with a higher speed rating than the existing tyres but never fit tyres with a lower speed rating.
Make sure you carefully check the service description whenever you change the tyres for a safer ride.