The wet grip rating is the safety heart of the tyre label. It measures how well a tyre stops on a wet road, and of the three ratings it is the one most worth paying attention to.
What it measures
Wet grip on the label means one specific thing: straight-line wet braking performance. A tyre is tested for how quickly it brings a car to a stop on a wet surface, and graded on that alone. The scale runs from A, the shortest wet braking distance, down to E, the longest, on the current label (the older scale ran A to G).
Because it is measured the same way for every tyre, it gives a fair head-to-head comparison of wet stopping ability across brands and models.
How much it matters
The difference between grades is not academic. Between the best and worst grades, the gap in wet braking distance from 50mph is around 18 metres, well over a car length, and on some measures closer to four or five. Each grade step is worth roughly a car length of stopping distance.
In an emergency stop in the rain, that distance decides whether a car halts short of the vehicle ahead or runs into it. For everyday driving in a wet climate, the wet grip grade is the single rating where paying for a higher mark most clearly buys safety.
Its limits
The wet grip grade is valuable but narrow. It covers straight-line braking only, not grip through wet corners, not resistance to aquaplaning in standing water, and nothing about dry performance. A tyre with a strong wet grip grade is a good sign, but it is not a guarantee of all-round wet ability, which is where independent tests that measure cornering and aquaplaning add to the picture.
Wet grip and tread depth
One important real-world point sits outside the label entirely: the rating is measured on a new tyre. As a tyre wears, its wet grip falls, because shallower tread clears less water. A tyre that left the factory with an A grade will not stop like one once the tread is low, which is why keeping an eye on the tread against the wear indicators matters as much as the grade it started with. When the tread is low, replacing the set with a strong wet-grip grade restores the performance the label describes; the grade is one of the figures shown against every tyre when you shop for a set online, so a strong one is easy to choose when buying online from a tyre seller like Tyres.co.uk.
From the workshop: if a customer asks where to spend on the label, we point straight at wet grip. In the British climate it is the grade that earns its money, but we always add that a worn A-rated tyre will not stop like a new one, so tread depth has to be kept up too.
Sources and accuracy. The wet grip scale and the roughly 18-metre figure between the best and worst grades reflect the published tyre-labelling test standards at the time of writing. Real stopping distances vary with the road, the car and conditions. If anything here looks wrong, get in touch and we will check it and put it right.
Common questions
What does the wet grip rating mean on a tyre?+
It measures how well a tyre brakes in a straight line on a wet road. Tyres are graded from A, the shortest wet braking distance, down to E, the longest. It is widely considered the most important safety rating on the tyre label.
How much difference does the wet grip grade make?+
A lot. Between the best and worst grades, the difference in wet braking distance from 50mph is around 18 metres, well over a car length. In an emergency stop, that gap can be the difference between stopping in time and a collision.
Is an A wet grip rating worth paying more for?+
For most drivers, yes. Wet braking is a core safety feature, and a higher grade brings shorter stopping distances in the rain. The extra cost of a top-rated tyre often buys a meaningful safety margin compared with a lower-rated one.
Does the wet grip rating cover grip in corners?+
No. It measures straight-line wet braking only. It does not rate cornering grip in the wet, resistance to aquaplaning, or dry performance, so a good wet grip grade is reassuring but not a complete picture of a tyre's wet ability.