Tyre load index and speed rating explained
5 min readBy Wheel Fit
The short answer: the number is the load index (weight per tyre) and the letter is the speed rating. Never fit lower than the vehicle manufacturer specifies. Fitting higher is usually harmless but rarely worth paying for.
Load index
The load index is a code, not a weight in kilograms. Each number maps to a maximum load per tyre:
| Index | Max load per tyre |
|---|---|
| 82 | 475 kg |
| 88 | 560 kg |
| 91 | 615 kg |
| 95 | 690 kg |
| 100 | 800 kg |
| 104 | 900 kg |
Multiply by four for the vehicle total, though that assumes even loading, which real life rarely provides. This is why vans need commercial-rated tyres: a loaded Transit puts far more through each corner than a family hatchback.
Speed rating
| Letter | Maximum speed |
|---|---|
| Q | 100 mph |
| T | 118 mph |
| H | 130 mph |
| V | 149 mph |
| W | 168 mph |
| Y | 186 mph |
The obvious question: why does a UK car need a V rating when the limit is 70? Because the rating is not only about top speed. It reflects how much heat the construction can shed and how the tyre behaves under sustained load. A higher-rated tyre generally has a stiffer casing and responds differently to steering input.
Why mixing ratings is a problem
Fitting below the manufacturer's specification can affect your insurance and will be picked up at an MOT if it makes the vehicle unroadworthy. More practically, mismatched ratings across an axle mean the two tyres behave differently under hard braking — which is exactly when you want them behaving the same.
Our rule: match what the door plate says, and keep both tyres on an axle the same specification.
Winter tyres are the exception
Some vehicles are permitted a lower speed rating on winter tyres, provided a sticker inside the car states the reduced maximum. Check the handbook rather than assuming.
Related: how to read the rest of the sidewall and why van tyres are different.
