Aquaplaning — it always sounds like something that you might do on a Mediterranean beach holiday. But aquaplaning in your car is no fun at all. At best it’s alarming; at worst, it can result in a serious accident.
After the recent deluges in the UK, aquaplaning is a particular hazard. In this post, we at what causes it and how to avoid it.
What is aquaplaning?
Tyres normally do a pretty good job at dispersing water. That’s important, because water acts as a lubricant between the tyre and the road surface, reducing traction and therefore the control you have over the vehicle.
However, under some circumstances, the tyre can’t disperse water quickly enough. Water pressure in front of the tyre builds up, creating a ‘wedge’ of water that lifts the front edge from the surface. This is aquaplaning. With reduced or zero contact with the surface, the tyre is skating over the water surface.
When one tyre aquaplanes it’s bad enough, with the vehicle’s handling becoming unpredictable. If all four tyres lift off, you’re now piloting a speedboat.
Factors in aquaplaning
The likelihood of aquaplaning is affected by all sorts of factors, some of which aren’t under your control. The depth of water on the road is obviously important, together with its camber and the smoothness of the surface. Salt on the roads also affects aquaplaning, as it raises the density of water, making it harder for tyres to disperse.
However, we’ll look at five key factors that are in your control, as they’re to do with the vehicle and how it’s driven.
- Vehicle weight. Other factors being equal, lighter vehicles are more likely to aquaplane. With less weight pushing the tyre into the road surface, it’s easier for the ‘water wedge’ to lift it.
- Tyre pressure. Under- or over-inflation alter the size and shape of the contact patch between road and tyres. Both can make aquaplaning more likely.
- Tread design. The tread patterns that manufacturers provide are optimised for different motoring conditions.Whilst all tyres are designed to disperse water, variations in tread design mean that some do a better job of it.
- Tread depth. As tread depth decreases, the tyre’s ability to clear water away falls drastically.
- Speed. The most crucial factor. At low speeds, even worn tyres with less-than-optimal tread patterns can disperse sufficient water to prevent aquaplaning. As vehicle speed rises, it becomes increasingly difficult to prevent.
What should be apparent from the list above is that there are a number of steps you can take to lower your risk of aquaplaning.
Top of the list is keeping your speed appropriate for the conditions. OK, you may not be able to predict the precise road conditions ahead. But we can all see when it’s been raining heavily, and that alone should be a signal to reduce speed.
Next up is keeping your tyres in good condition. We’ve blogged before about the dangers of part-worn tyres. Though the legal limit for tread depth is just 1.6mm, tyres start losing their water-dispersing abilities well before that. Maintaining a decent tread depth — many suggest at least 3mm — massively reduces the risk of aquaplaning. Keep your tyre pressure close to the manufacturer’s recommendation, too. It may not do wonders for your fuel economy, but it will give your tyres the best possible chance of clearing away water.
Lastly, if aquaplaning is a concern (and given the conditions in the UK, it should be), make the tyre’s wet performance a factor when you’re buying your next set. EU tyre labelling tells you how each tyre is rated for wet performance on an A – E scale. For example, Dunlop Sportsmaxx RT tyres are A-rated. There are plenty of tyre reviews to help you choose. Evo magazine recently tested a range of premium tyres for curved and straight aquaplaning. Dunlop Sportsmaxx were the best performers in their curved test, and Michelin Pilot Sport 4s topped their straight test. If you’re still unsure of what to go for, ask a friendly professional.
One thing’s for certain, with Britain’s weather getting more extreme, the risk of aquaplaning isn’t going anywhere — so make sure you do what you can to avoid it.