Wet Weather Driving — Aquaplaning
To explain what aquaplaning is all about we need to go off on a bit of a tangent for a moment, but don’t worry, as there is some significance in what follows.
If you were to go out onto a freshly formed snowdrift, and stand on the top of it on a sheet of board, you could jump up and down on it without sinking. If you stepped off your board you would sink up to your crotch in snow, as your feet do not have a sufficiently large enough surface area to keep you on top of the snow.
Your ability to stay on top of the snowdrift will be due to the board spreading your body weight over a large surface area and so prevent you from sinking.
Applying the same principles to your car. If you drive a model that has nice wide sporty tyres these will provide you with lots of good grip for cornering on a dry road.
However, in very wet driving conditions the car may well be worse to drive than one with skinny tyres. The problem with tyres that have a large footprint there is more rubber to skim on the surface of the water.
By spreading the weight of your car over a larger surface area of road, as will be the case with wide tyres, by comparison to narrower tyres there is greater potential for the car to suffer from aquaplaning, even in mildly wet driving conditions.
Tyre Grip is Created by Friction Created by Downforce
Cars tyres grip the road through friction between the rubber and the road surface, and that friction is created by down force. In the case of a road car, down force comes from the actual weight of the vehicle being pulled onto the road surface by gravity. Like the example of standing on a board on a snow drift, the wider the tyre the actual down force per square millimetre of its footprint will be less than that of the surface area of a narrow tyre footprint if fitted to the same car.
Aquaplaning is a condition whereby the tyres of a vehicle lose physical contact with the road surface as they begin riding on a layer of water, in much the same way as a surfboard will skim over the surface of a wave.
This occurs when a vehicle is being driven on a wet surface at such a speed the tyre tread pattern is unable to disperse the surface water from beneath it quickly enough. Aquaplaning will be a more likely event if your car has worn tyres, because the more shallow the grooves the less capable the ability to clear the water from beneath it.
Steering Control is Lost During Aquaplaning
If the effect of aquaplaning occurs upon the front tyres, which it nearly always does, the driver will lose all steering control, as well as any braking effect at the front wheels.
Rear tyres are far less likely to aquaplane, because they have less water to disperse. This is because the rear tyres run in line with those at the front, and as the front tyres cut a swathe through the surface water on the road, this creates a channel of clearer tarmac for the rear tyres, making aquaplaning at the back unlikely.
If the rear tyres did aquaplane it would be long after the front end had lost out, and by that time it wouldn’t matter a jot whether the rear of the car was gripping the road or not.
How do you know if you are aquaplaning or not?
Firstly, there has to be water on the road surface, and usually lots of it. We’re talking heavy downpour stuff here, or a large amount of standing water from earlier rainfall, or from some other source. The first thing to notice is the front of the car will become very light, as if driving on ice, and you can feel this through the steering. Now you know you have no grip at all at the front of the car and this is not the time for making sudden movements – or any movements at all actually.
An Aquaplaning Situation is Often Made Worse by The Driver
Aquaplaning can be a terrifying experience, and all too often, when a vehicle aquaplanes, the vehicle will go into a spin. This may happen even if the incident occurs on a straight section of road and usually because the driver has done something to make matters worse.
Once the grip of the tyres is lost, the direction of travel of the vehicle becomes subject to the force or forces acting upon it. It will naturally follow the camber of the road, for example, or any gradient that is present.
When a the average motorist realises their vehicle is aquaplaning they usually panic.
A driver becoming alarmed at the behaviour of the car will usualy and instinctively snap their foot off the gas pedal, which immediately changes the balance of the car. It is now the car may begin to head off course.
The usual response of the driver to the slight change in course is to move the steering wheel, which now further disturbs the balance of the car. This will usually be followed by an application of the brakes, or some other reactionary process, from which stage the situation will usually have developed beyond the point of return. Now the vehicle will be completely out of the control of the driver.
You will have read somewhere before, or heard someone say, that if your car is affected by aquaplaning you are to gently reduce speed by easing off the power. That is very nice advice in theory, but the reality is the average motorist won’t ease off the power, as they will just snap off the gas, because the aquaplaning situation will startle them. However, there is a better course of action, such as this.
Don’t Make Any Sudden Moves, But Freeze Everything
As soon as you feel the car begin to aquaplane just freeze everything as you are. Lock your accelerator foot solid in a neutral throttle zone, this being a state where the engine is neither accelerating or decelerating the car. Keep your arms locked on the steering wheel in a straight ahead position and just wait. In a few seconds you will be through the water the has caused you concern and with tyre grip restored.
Changing the balance of the car at the point of aquaplaning will provoke something else to happen rather than cure it. In more cases than not, the reason you have suddenly begun to aquaplane is due to running into a patch of water on the road that is slightly deeper than elsewhere, or you have begun to significantly increase speed within existing wet conditions.
However, if you have caused the car to go significantly out of line, by trying to counter an involuntary or unwanted change in direction, and it is absolutely necessary to make a correction, make the tiniest and the very most gentle of steering movements. In addition to this, and if you are driving a manual transmission vehicle, bang the clutch pedal down (no brake) to neutralise the transmission.
If you have a vehicle with automatic transmission, then it is okay to gently lift off the accelerator. With an automatic gearbox in ‘D’ there is practically no drag effect on the drive wheels by doing this and so it shouldn’t get you into further trouble.
As well as not making any steering movement, if any braking is done at any time the tyres are skating on water, remember how this will also make things worse. Therefore, do not make any sudden speed changes in any way, shape or form.
Aquaplaning Usually Only Lasts a Few Seconds, So Stay Calm
A period of aquaplaning, for 99% of occasions, will be no more than for a second or two and will usally occur in places where the camber of the road swaps over, causing surface water to flow across to the other side. This creates a band of deeper water a few feet long, or it may be you have hit a large–ish puddle in the road.
Whatever it is, and in real terms, even when travlling at normal driving speed, you are going to be through the problem in a couple of seconds, after which your tyres are back on a more reasonable footing. By going rigid at the controls you should be able to ride it out and with no harm being done.
Once the moment is over, and your tyres are back in contact with the road, then is the time to reduce speed or make whatever corrective changes are necessary, but not when you are actually aquaplaning. However, if you have gone into a complete spin you will be beyond the point of return, and then you are best just to tread heavily on the brake and brace yourself for the crash.
Yes, you have always been told that when you get into a skid you are not to brake, but when you get into something this crazy, unless you have the experience or the extraordinary skills to do otherwise, you will not intentionally pull out of it. All you can hope for is the car will have lost as much momentum as possible before it hits something and heavy braking might just help with that.
As it has been said before on this and other pages within this series of driving tips, it is not the initial stages of an incident that will cause loss of control of the vehicle, or cause you to crash. It will be what you do in response to the incident that will become the problem. The general rule is that in an emergency such as this, is the first thing to do is don’t, and that will probabaly get you out of more situations than anything else.
Ride Drive Limited
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Wet Weather Driving — Aquaplaning