The 91V on the end of a tyre size is not part of the size itself; it is the tyre's two key limits. The 91 is the load index, and the V is the speed rating. Together they tell a driver how much weight each tyre can carry and how fast it is built to go.
91: the load index
The load index is a code for the maximum weight a single tyre can carry at its correct pressure. It is read from a standard load chart rather than being the weight itself. On that chart, 91 equals 615kg per tyre.
Multiplied across four tyres, that covers the car's weight including passengers and luggage, with margin built in. The car maker chooses a load index to suit the fully laden car, which is why a replacement should never drop below it. Heavier cars, electric vehicles and people carriers often need higher figures, sometimes paired with an Extra Load casing.
V: the speed rating
The speed rating is a letter standing for the maximum speed the tyre is constructed to sustain safely. V equals 149mph (240km/h). The common ratings around it are:
| Rating | Max speed |
|---|---|
| T | 118mph (190km/h) |
| H | 130mph (210km/h) |
| V | 149mph (240km/h) |
| W | 168mph (270km/h) |
| Y | 186mph (300km/h) |
The rating reflects the tyre's construction limit and the heat it can handle at sustained speed. It is not an instruction to drive at that speed, and on UK roads the figure is always well above the legal limit. What matters is not fitting a tyre rated below the car maker's specification.
Why the rating must not drop
Load index and speed rating are matched to the car. Fitting a tyre with a lower rating than specified can leave it working beyond its safe limit under load or at speed, which is a genuine safety risk. It can also create problems with an insurer after a claim, and a tyre clearly unsuitable for the vehicle can be flagged at the MOT. Fitting a higher rating, by contrast, is normally acceptable.
Finding the right figures for a car
The correct load index and speed rating are listed on the placard inside the driver's door and in the handbook, alongside the recommended tyre size and pressures. Where a fitted tyre shows a different rating from the placard, the placard is the specification to follow. When a replacement is due, a registration search at Tyres.co.uk and other online tyre retailers brings up only tyres that carry at least the right load index and speed rating.
A higher number is not a complete upgrade
A proposed replacement with a higher load index still needs the correct size, construction and vehicle compatibility. It may also have different inflation requirements for a given load. Do not accept a lower specification simply because the car is lightly used. If the fitted tyre and the vehicle documentation disagree, ask the fitter to establish the required specification rather than assuming 91V is correct because it is already on the car.
Common questions
What does 91V mean on a tyre?+
91V combines two ratings printed after the tyre size. 91 is the load index, meaning each tyre can carry up to 615kg. V is the speed rating, meaning the tyre is rated for speeds up to 149mph (240km/h).
What does the 91 mean?+
91 is the load index, a code for the maximum weight one tyre can carry at full inflation. On the standard chart, 91 equals 615kg. The figure for all four tyres together covers the car's fully laden weight.
What does the V mean?+
V is the speed rating, the maximum speed a tyre is built to sustain. V equals 149mph or 240km/h. The rating is about the tyre's construction limit, not a suggestion to drive at that speed.
Can I fit a higher rating than 91V?+
Yes. A higher load index or speed rating than the car maker specifies is generally fine. Fitting a lower rating is not, as it can leave the tyre under-rated for the car's weight or performance, and may affect insurance and the MOT.