Winter driving: why does my car aquaplane?
Heavy rain, snow and slush can considerably reduce the grip your tyres have with the road. Here's how to reduce the chances of aquaplaning
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You won't need us to tell you that Britain gets its fair share of rainfall during the winter. In some regions, you can add snow, ice and that horrible slushy combination of both to the list of challenges motorists face.
When the road is saturated by any of the above, aquaplaning becomes a real risk - and that's something we should be cautious about. But what exactly is aquaplaning?
Aquaplaning - the basics
Aquaplaning is when the tread in your car tyres can’t clear the water, snow or slush that’s beneath them fast enough. The water builds up in a little wave ahead of the tyre, until there’s too much for the tread to clear and the tyre “planes” across it. Your tyres are no longer in contact with the road and you can’t brake or steer. It feels like sliding on ice - scary.
What causes aquaplaning?
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1) Standing water
Large amounts of water on the road surface is the main cause. Without water on the road, aquaplaning simply can’t happen.
If the road ahead isn’t draining and there are puddles, the likelihood of aquaplaning increases. The more water on the surface, the less chance your tyres have of clearing it and staying in touch with the tarmac.
Obviously, if there’s a major flood then you shouldn’t attempt to cross the water at all.
2) Worn tyres
If your tyres are worn, the channels in the tread that are designed to clear water are reduced in depth and aquaplaning is more likely to occur even.
Tyres have horizontal wear indicators in the tread so make sure you check these. Or you can use a 20p coin instead. The tread on your tyres should be deeper than the outer band of the coin. If it isn’t then it’s time to buy some new rubber.
3) Incorrectly inflated tyres
Tyres are designed to operate effectively at specific pressures. These do vary from car model to car model, and tyre brand to tyre brand, so check your handbook for the correct pressure.
If your tyres are under-inflated then the contact patch with the road won’t be as designed and the tread can’t dissipate water as intended.
Keeping up with regular car maintenance can help avoid this issue.
4) Wrong tyres
In Britain, our winter weather is rarely extreme so few drivers make the switch to winter tyres. Instead, we generally run with either summer tyres or all-seasons and most of the time that’s fine.
However, some high-performance tyres, while still road legal, do not do so well in the wet. Some road-legal tyres are even specifically designed to perform on dry racing circuits (they're popular with supercars) and simply don’t have the ability to clear water like regular road tyres.
If you live somewhere that gets particularly bad weather, you should consider winter tyres.
5) Speed
Your poor tyres have a lot of work to do in the rain and the faster you go the harder you make it for them.
Slowing down will help give them a chance to do their job better and avoid aquaplaning altogether.
Driving within the speed limit is also safer and better for fuel efficiency, so it's a win all round.
How to avoid aquaplaning
You’ve fitted the right tyres, checked the tread depth and pressures, and reduced your speed while driving in the rain, what else can you do to avoid aquaplaning?
Keep your distance from the car ahead to stay out of the spray and get a clearer view of the road. Hanging back gives you more time spot puddles of standing water, which usually form in dips in the road or at the bottom of hills, and reduce your speed further for the best chance of getting through without flying.
Should the car ahead of you aquaplane, then more distance means you’ve also got more time to react and avoid a potential accident.
To gauge a safe following distance, use the “4 second rule”. Observe the car in front passing a fixed point and count four seconds. If you’ve passed the same marker before you get to four then you’re too close.
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Do all-wheel drive cars and 4x4s aquaplane?
Front-drive, rear-drive or all-wheel drive, it won’t make a difference. Even off-road-ready 4x4s can't escape it - they can all aquaplane.
Aquaplaning is purely down to the tyres, and the amount of water on the road. The traction advantage of an all-wheel drive car is only there when the tyres actually connect with the road.
Imagine giving a mountain goat a pair of stilettos to tackle its home terrain. Whatever car you drive you need to make sure the right boots are fitted.
What does it feel like when you aquaplane?
If you aquaplane, it will happen fast and the only real sense you’ll get that it’s happening is through the steering wheel.
You’ll get the feeling that the steering is extra light. Don’t be tempted to over steer or make sharp movements. You may also hear the engine revs rise as the tyres spin on the water’s surface.
What to do if you aquaplane?
Once your car is actually aquaplaning, you’re essentially just a passenger and there’s little you can do until the tyres get their grip back.
Keep the steering wheel straight and don’t be tempted to brake.
Ease off the accelerator and sit tight, even if your car is drifting slightly left or right.
Once you clear the water, the tyres will grip again and it’s at this point you can brake or apply corrective steering inputs.
If you do turn the steering wheel while skimming the water’s surface you could suddenly swerve or spin when the tyres bite again. It'd be like sliding off the ski slope and hitting tarmac - the grip change will be sudden. As a result. braking can also cause a more sudden deceleration than you intended when tyre and tarmac meet again, which could lead to a loss of control.
In short, if you do find yourself aquaplaning, be as smooth and careful as you can with all inputs. But in order to reduce the chances of this happening, best to drive more slowly, and be certain you have a healthy, correctly-inflated set of season-appropriate tyres.