Cruise control - a no-no in wet weather

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Cruise control - a no-no in wet weather

Postby CrazyChick » Wed 20 Mar, 2013 12:39 am

Recieved an email about the dangers of using cruise control in wet weather, below is what was contained in the attached pdf.

SAFE-DRIVING TIPS WHEN IT IS RAINING!

A good tip:

A 36 year old female had an accident several weeks ago. It was raining, though not excessively when her
car suddenly began to hydro-plane and literally flew through the air. She was not seriously injured but
very stunned at the sudden occurrence! When she explained to the Police Officer what had happened, he
told her something that every driver should know -

NEVER DRIVE IN THE RAIN WITH YOUR CRUISE CONTROL ON.

She thought she was being cautious by setting the cruise control and maintaining a safe consistent speed
in the rain...

But the Police Officer told her that if the cruise control is on, your car will begin to hydro-plane when the
tyres lose contact with the road, and your car will accelerate to a higher rate of speed making you take off
like an aeroplane. She told the Officer that was exactly what had occurred. The Officer said this warning
should be listed, on the driver's seat sun-visor - NEVER USETHE CRUISE CONTROL WHEN THE
ROAD IS WET OR ICY, along with the airbag warning. We tell our teenagers to set the cruise control
and drive a safe speed - but what we don't tell them is to use the cruise control only when the road is dry.
The only person the accident victim found who knew this, (besides the Officer), was a man who'd had a
similar accident, totalled his car and sustained severe injuries.

NOTE: Some vehicles (like the Toyota Sienna Limited XLE) will not allow you to set the cruise control
when the windshield wipers are on.

Even if you send this to 15 people and only one of them doesn't know about it, it's still worth it. You may
have saved a life.
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Re: Cruise control - a no-no in wet weather

Postby Mac » Fri 22 Mar, 2013 1:58 am

Erm... I don't think this is wholly accurate.

When a car aquaplanes it is due to the interaction of the tyre, water a road surface.

When the volume of water exceeds the pumping action of the tyre tread, the rolling radius of the tyre pumps more fluid under the tyre increasing the fluid pressure until the car hydro-dynamically is lifted on top of the water.

Usually happens around 50-60mph on a road car depending on volume of rain, tyre tread pattern.

The car's forward motion is enabld by to motive force applied by the drive train and trugh the tyres to the road surface.

Following Newtons second law, Force = mass x acceleration (and the conservation of energy principle) + work done against friction.

With the car losing traction, there is therefore less force to overcome the friction of aerodynamic drag and thus deceleration would occur; Not as the policeman said, would you speed up.

While there would be less friction between the road surface a tyre due to the low shear properties of water, this would still only result in yaw of the car and a sensation of speeding up as a 'loss of control' is perceived.

The likes of Lewis Hamiltion, or Jenson Button, Senna or other such notable wet weather drives will feel the transitional state of the hydrodynamic pumping of the water beneath the tyre and thus tiny yam moments.

They are more likely to mental 'filter out' minor disturbances, and thus would more likely feel that the car actually slows down when the car aquaplanes and regains traction as the tyre begins pumping fluid away from underneath the tryre contact patch.

If ever you are driving and feel the car going light on the steering, or feel tiny yaw moments, then simply stop what your doing, be that braking, accelerating or just dab the throttle/brake/ and turn off the cruise control, the car will regain its composure quickly enough.

Of course if you've been driving like a complete "expletive", then that tiny yaw may well become a big on and see you spinning into the ditch
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Re: Cruise control - a no-no in wet weather

Postby Pepper » Fri 22 Mar, 2013 9:19 pm

Think this has done the rounds a couple of times.... it has been poo - poo'ed every time as well


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