Tyre Speed Rating Explained

A tyre's speed rating is the single letter at the very end of the size, after the load index. It codes for the maximum speed the tyre is built to sustain safely. In a size ending 91V, the V is the speed rating, and it means the tyre is rated to 149mph (240km/h).

What the rating actually describes

The speed rating reflects how much heat a tyre can handle at sustained high speed, which comes down to its construction and materials. It is a built-in limit, not a target. On UK roads every common rating sits well above the national speed limit, so the rating is about safety margin and matching the tyre to the car, rather than anything to do with how fast a car is driven day to day.

The speed rating chart

The letters relevant to cars run as follows:

The one quirk worth knowing is that the order is not strictly alphabetical: H sits between U and V, a historical hangover from when H was the only high-speed rating. A bracketed rating such as (Y) indicates a tyre certified above 186mph. Lower letters than N exist for specialist, temporary and off-road tyres, but they are rare on ordinary cars.

ZR and the old Z marking

Some performance tyres carry ZR within the size, for example 225/40 ZR18. This is an older way of flagging a tyre rated above 149mph. On modern tyres the precise limit is given by the W or Y letter at the end, so the ZR is largely a legacy marking that signals a high-performance tyre.

Choosing the right rating

The rule mirrors the load index: a replacement should carry at least the speed rating the car maker specifies, shown on the door placard and in the handbook. Fitting a higher rating is generally acceptable. Fitting a lower one is not, because it can place the tyre beyond its designed limit, and a tyre clearly unsuited to the car can create problems with an insurer and at the MOT.

One sensible exception is winter tyres, where it is widely accepted to drop the speed rating, often to a Q or H, because winter rubber is not built for the same sustained speeds and the car is driven accordingly in winter conditions. Even then, the load index should be maintained.

Mixing speed ratings

Matching all four tyres is the proper approach. Where ratings differ, the lowest-rated tyre effectively sets the safe limit for the whole car, and mismatched grip front to rear can affect handling, particularly in the wet. If a mismatch cannot be avoided in the short term, the safest arrangement is to keep matching pairs across each axle, and to replace with a full matching set as soon as possible. Tyre retailers such as Tyres.co.uk let you search by size, bringing up only sets that carry at least the speed rating the car needs.

From the workshop: the speed rating spooks people because of the mph figure, but the only thing that matters is not going below what the placard says. The one time we routinely fit a lower rating is winter tyres, and that is by design, not a shortcut.

Sources and accuracy. The speed rating figures on this page follow the standard industry speed rating table used across the tyre trade, and are given as a general guide. The definitive speed rating for any specific car is the one on the placard inside the driver's door and moulded on the tyre's own sidewall. If anything here looks wrong, get in touch and we will check it and put it right.