It’s a scenario that many drivers will recognize: One minute there’s not a cloud in the sky and the next it’s pouring down. Clouds of spray bring a sharp reduction in visibility, accompanied by the sound of water being flung against the wheel arches. A sudden increase in engine noise tells you the tires have lost contact with the road, and the car is no longer steerable. This is not the time to tug the steering wheel around. If the wheels are pointing too far left or right when the tires get back in touch with the road, the car will swerve and skid, making things more dangerous than ever. Even driver assistance systems are largely powerless to help, because in order to work effectively they need the tire/road contact that has just disappeared.
Sudden downpours and thunderstorms are even more hazardous in summer. Accustomed to dry road conditions, drivers tend to assume that braking distances will be as short and handling as precise as ever. But in next to no time they will find that both the brakes and the steering need a more delicate touch. Larger areas of standing water and long ruts are clear and present dangers, but there are others, too: Over days and weeks of dry weather, the road surface can acquire a coating of pollen, resins and dust thrown up by tractors and harvesters. Add rainwater and this cocktail has the same effect as liquid soap – as motorbike riders know better than most. “At times like this, the only things that help are lower speeds, a generous safe distance from the vehicle in front, lights switched on and a careful hand on the steering wheel,” says Angelo Perez-Riemer from the Contidrom, Continental’s proving grounds north of Hanover. “If aquaplaning sets in, the ideal response in a stick-shift model is to immediately depress the clutch. In electric vehicles and automatics, keep the gas pedal steady and avoid braking or heavy-handed steering while the danger lasts. If you’re caught in a deep rut, even 80 km/h can be too fast. With a truck coming up fast in the rear-view mirror, stress levels can peak, accompanied by a deep-rooted desire to hit the gas and escape the danger. But that’s the wrong reaction. It’s far better to stop at the next rest area and wait until the worst is over.”
It also helps if your tires have a safe amount of tread. “The less tread depth you have, the less water can be taken up by the grooves and dispersed, so the car is more vulnerable to aquaplaning,” says Perez-Riemer. “Tests with a typical PremiumContact 6 car tire in size
205/55 R 16 showed that, with eight millimeters of water on the road, a brand new tire delivered safe handling up to 86 km/h, while a tire with three millimeters of tread left stayed in contact with the road until just over 67 km/h. With the bare legal minimum of 1.6 millimeters of tread remaining, the onset of aquaplaning came at 48.5 km/h – a speed often reached around town. That’s why we always advise drivers to make sure their tires still have well over the legal minimum of 1.6 millimeters of tread.” But tires are not the only rubber products that need to work reliably in a car: Because if the wipers draw streaks across the windshield instead of delivering a clear view, visibility will drop, reaction times will rise, and the dazzle of oncoming headlights will get worse. So drivers are well advised to check the weather forecast before leaving home, plan to take breaks when traveling in the wet, and leave plenty of time for the journey.