Every tyre has what’s known as a load rating or load index. It’s vital to fit tyres with the correct load index for your vehicle to guarantee maximum tyre life and ensure your car is as safe as it can be.
What is a tyre load rating?
The load rating or index is how much weight an individual tyre can support. The tyre’s load rating comes in the form of a number. This number relates to the total weight in kilograms a tyre will support.
Each tyre must be able to carry half the weight borne by the axle it is mounted on. If for example, a tyre has a load rating of 90, it will support 600kg as a single tyre or 1200kg across a two-wheel axle.
Why is tyre load index rating important?
The correct load rating for tyre and vehicle combination is essential. A tyre that hasn’t been built to carry the load you’re asking it to is more likely to fail. This is because the tyre sidewall will be put under more stress than it was designed for.
This can be downright dangerous because it increases the chances of a sudden failure or blowout. If an insurer can prove tyre failure was a result of it not having the correct load rating, it might be able to get out of paying for any damage that ensued.
MOT testers are required to check the load rating of a vehicle’s tyres and tyres with the wrong load rating will fail.
How do you find the correct tyre load index for your vehicle?
The first thing to do is to check your car’s user manual. Don’t simply go by the load rating on the tyres your car is currently fitted with. The reason for this is you can’t be certain that the previous owner fitted the correct tyres.
Every tyre has a series of markings on its sidewall. These contain crucial information such as the wheel size, width of the tread and height of the sidewall. The load index forms part of this. It is expressed as a pair of digits immediately after the size information. So if the characters on a tyre read 225/35 R18 90 W, the 90 is the load index.
How do you interpret tyre load index?
Figuring out the load rating isn’t made any easier because it is in the form of apparently random digits. In fact these relate to the number of kilograms a tyre can support. The lowest load index of 70 can support a total axle weight of 670kg or 335kg per tyre.
The best way of understanding tyre load is to go to a table that translates it into weight. You can find out exactly what load ratings on the tyre load index chart in this article by the government. But remember the weight it gives is for a complete axle.
How do you choose the right tyre load rating?
First you need to know what the load rating for your vehicle is. You will find this in the vehicle’s user manual.
Make sure that you’re looking at the correct specification for your car when you’re trying to find the load rating. You then need to find tyres that are compatible with your car and have the right load rating.
Check your vehicle manufacturer’s recommendations
The user manual will probably tell you what make and type of tyre your car was fitted with when it left the factory. These will have been optimised by the tyre manufacturer to offer the best performance for that vehicle.
As you will discover when you start looking around at tyres, not every tyre in the size that’s right for your wheel comes with the correct load rating for your car.
And then there are budgetary considerations. You might want to buy different tyres to the ones the car is already fitted with, perhaps to save money. Whatever you choose, they must have the same or a higher load rating than the tyres the manufacturer specifies, or the ones it was originally fitted with when it left the factory.
I’ve been writing about cars and motoring for more than 25 years. My career started on a long-departed classic car weekly magazine called AutoClassic. I’ve since pitched up at Autosport, Auto Express, the News of the World, Sunday Times and most recently the Daily Telegraph. When I’m not writing about cars and motoring, I’m probably doing some kind of sport or working in my garden.