What is aquaplaning and how can you prevent it?

Rain is a blessing, at least: for agriculture. But for motorists it is more like a curse. For example, because of the constantly swishing wipers in front of you and the poor view of the road. The greatest danger is formed by the water on the road surface; if you as a driver do not adjust your speed in time, the tires will lose contact with the road. At a certain point you slide more over the water film on the asphalt than you drive through it: a clear case of aquaplaning. At such a moment you lose control of your car, a life-threatening situation.

What actually happens during aquaplaning?

The bottom line is that the tire profile is no longer able to drain the large amount of water over the tread. In fact, at that moment the profile behaves like a channel system that is flooded by a tidal wave. The water forms a layer under the tires and the grip on the road is lost. Steering and braking movements are then no longer transmitted.

At what speed a tire loses contact with the road depends of course on the tire itself. There are major differences between them on this point our tire tests be judged heavily. The speed at which tires start aquaplaning is determined by the tread depth and the amount of water on the road. A simple rule of thumb: the more water on the road, the smaller the residual profile in the tyres, the faster road contact is lost. The legal requirement that the profile must be at least 1.6 millimeters deep is in fact quite inadequate. Because it takes very little for the shallow channels to overflow into a worn profile. It is therefore unwise to continue driving until the legal profile limit has been reached. If the road noise and steering forces of the car change noticeably when driving on a wet road surface, slow down. See also the other tips on these pages.

Expert tip

When aquaplaning on a straight road, the car no longer reacts to steering movements and braking is only possible to a limited extent. If a car loses contact in a curve, you slide to the outside of the curve, without being able to countersteer. Aquaplaning can be prevented by reducing the speed on a wet road and by making sure that the winter tires have the tyres tread depthat least four millimeters. And with summer tires you can safely stick to 3 mm. You can easily measure that yourself. Do that regularly too! In addition, a good one helps tire pressure: if there is more air in the tires, the contact surface, which carries the mass of the car, with the road is smaller. The water is then better drained. And that helps to keep a grip.

Where does aquaplaning occur?

In general, especially on roads where rainwater cannot drain away fast enough, there is a risk of aquaplaning. This may be due to geographical circumstances, for example if the road is the lowest point in the area. It can also be a bend with insufficient slope on the sides. But damaged asphalt with deep irregularities or ruts from freight traffic also pose a risk. You should also be careful on roads with many trees in the area. Or if there is no good water drainage along the road, so that grass, mud or weeds leave the water on the road.

Variable maximum speed

There are roads with a variable speed limit, such as the A1 between Bussum and Muiderberg. When busy, but also when it rains – and therefore a wet road surface – you are only allowed 100 instead of 120 km / h. The current maximum is automatically indicated on the relevant stretch of motorway. Also in Germany, for example, lower maximum speeds apply on wet road surfaces, indicated by the lower sign ‘Bei Nässe’. As a rule of thumb: if your predecessor leaves a visible trace in the water film on the road, the lower speed applies. If there is light rainfall, you can simply drive at the speed that applies to dry road surfaces.

Sample in parking lot

To see how the average motorist handles their tires, we carried out spot checks in large parking lots. The shocking result: of the sixty cars checked, nine did not meet the legally prescribed minimum tread depth of 1.6 mm. This can lead to a fine of €300. Even worse: the braking distance is already a lot longer in light rain and the car loses road contact much sooner than if new tires were mounted.

The ideal rain tyre

The ideal rain tire has a prescribed direction of travel, which drains the water from the tread to the side as quickly as possible. In addition, it has stable tread blocks that provide as much grip as possible. The profile channels should be at least three millimeters deep for summer tires and at least four millimeters for winter tires. To improve the grip of the rubber mix on wet surfaces, silica has been used as a filler instead of carbon black.

The best rear tires

To be clear: the driving behavior of a car is best if the profile depth of the four tires varies as little as possible. But if you are only replacing two tires, it is best to mount the tires with the most tread on the rear axle. The rear tires provide stability. Important: winter tires are often directional (recognizable by the arrow on the sidewall) or have a prescribed outside (the side then says outside). If the tires are mounted in the wrong direction, they are less safe.

Tips against aquaplaning

In case of aquaplaning, the tire can no longer push away the water layer. The tire then loses contact with the road. To avoid this:

• Check the tires for sufficient tread. It is advisable to replace summer tires at the latest at three and winter tires at four millimeters of tread.
• Regularly check the tire pressure. A soft tire drains the water less well. In addition, it wears faster and it ensures higher consumption.
• Reduce speed in heavy rain.
• Drive extra carefully on the right side of the road. There is a lot of water in the deep ruts left by trucks.
• In emergency situations: release the gas and do not make sudden steering movements.

AutoWeek Judgment

The tests we have carried out speak volumes: on a wet road, sufficient tread is an absolute prerequisite for safe driving. And we are not only talking about the length of the braking distance, but also about the degree of aquaplaning. A sense of responsibility is required from the motorist here – every millimeter of profile counts. So don’t drive to the legal minimum of 1.6 mm, but replace the tires sooner. Then you always play it safe. If you want to replace the tyres, find your new ones for the best price with the AutoWeek Tire Price Comparison.