Don’t lose your grip
AQUAPLANING (or hydroplaning) is when a tyre rides up on top of standing water on a road. At that moment, almost all grip is lost and it will not return until the car slows sufficiently for the tyre to cut through the water and regain contact with the road.
You may have seen pictures of our aquaplaning tests with long stretches of deep water and think this is not relevant to your driving. But you’d be wrong, because the moment your car seemingly jumps as it crosses a stream of water on a wet road is aquaplaning. The loss of grip may be short, but as the car skips, the cornering force is momentarily reduced to almost nothing.
You can also experience the same thing on a motorway where water has pooled in large areas and the car skates across it until it reaches drier parts. The reason it is more likely to happen on a motorway is that we drive faster there and speed is the key to aquaplaning.
Why? The best way to explain it is to think of the tyre’s tread (the key part here) as a pump. All those channels and grooves out to the sidewalls are designed to shift water to the front, back and sides, allowing the tread to remain in contact with the road. When the volume of water increases as the car accelerates, there comes a point when the ‘pump’ can’t cope and the tyre rides up on the water. When those channels are worn to near the legal limit, reducing the size of the ‘pump’, the tyres can’t shift as much water and perform poorly in the wet.
It may not be part of the EU tyre label ratings, but aquaplaning is a key safety factor and we include it in our annual tyre tests. Running with one wheel in the wet and the other in the dry, we measure the speed at which the former is spinning 15 per cent faster than the other while under hard acceleration. We also measure the loss of grip while cornering at ever-higher speeds to assess how well that tread performs when it’s distorted.
You might not experience aquaplaning that often in everyday driving, but when you do, you want a tyre that reduces that risk as much as possible.