Cruise Control and Aquaplaning

corktina

Saw a post on Facebook re the dangers of Cruise Control in times of low adhesion...surely it can't be true that there is a danger of the car accelerating with the wheels spinning and aquaplane out of control....surely Traction Control would sort that out straight away and I'm sure every car with CC must have it!

Urban Myth? I think so!

12 element

Seems true:

http://www.snopes.com/autos/techno/wetroad.asp

corktina

it would ease up once they reach the set speed maybe, wouldn't traction control kick in the instant the wheels were going faster than the road speed?

HandsomeDan

OSI wrote: »

If anything, the cruise control will ease off the accelerator. When your tyres lose traction, they speed up and as the CC takes it's speed from the wheels, it would think the car was going faster than the set speed and ease off the accelerator.

Yeah, I would have thought that was obvious, but if the internet says otherwise it must be true :rolleyes:

MugMugs

OSI wrote: »

And if you're already using cruise control when you hit the water, you'd already be at the set speed, so it would pick up on any change of speed, which in this case should be an increase so the CC would cut the power.

Being the key point!

jimgoose

OSI wrote: »

Well, to it the road speed is the wheel speed. Traction control works by detecting the difference in speed between each of the wheels. It's possible the driven wheels would spin up with the loss of traction as they would on ice, so it should kick in in some form, but only works if the wheels appearing to be accelerating. Stability controls are more likely to have an impact.

And if you're already using cruise control when you hit the water, you'd already be at the set speed, so it would pick up on any change of speed, which in this case should be an increase so the CC would cut the power.

Most of them apply the brake when speed increases, which you probably don't want in an aquaplaning situation either.

MugMugs

Any that I've ever used just ease off the gas.

hi5

This is true, it happens when you brake to slow down, then hit the resume button, it will accelerate (more than you would normally) to get back to the set speed, if you have a lot of power then any loss of traction can put you sideways very quick.
It happened to me once in the rain, scared the **** out of me:eek:

Dartz

Depends on the cruise control system, really - along with what wheels of the care are being driven by it and whether the car has TCS, or any other stability control system.

Anjobe

12 element wrote: »

Seems true:

http://www.snopes.com/autos/techno/wetroad.asp

Here's a rather more believable take on that same story...

tossy

This was circulating in the same e mail that claims driving with sunglasses on in the rain makes the rain invisible

When are we going to get a scare tactic/make believe e mail campaign on the correct use of indicators and lane discipline

corktina

you should NEVER use cruise Control in the fast lane with sunglasses on... :-)

Chippy01

A lot of older cars that have cruise control as standard (or retro-fitted), do not have traction control/vehicle stability control fitted.

Most modern cars now have both fitted as standard, which means that if the car starts behaving erratically under cuise control, the traction control will shut down the cruise and shut the throttle at the same time.

tin79

corktina wrote: »

you should NEVER use cruise Control in the fast lane with sunglasses on... :-)

Pffft, its the slow lane and a baseball cap. Thought everyone knew that.


If you call it the driving lane you can get away with it.

corktina

Chippy01 wrote: »

A lot of older cars that have cruise control as standard (or retro-fitted), do not have traction control/vehicle stability control fitted.

Most modern cars now have both fitted as standard, which means that if the car starts behaving erratically under cuise control, the traction control will shut down the cruise and shut the throttle at the same time.

most modern cars do not have cruise control even as an option as far as I know

jimgoose

Chippy01 wrote: »

A lot of older cars that have cruise control as standard (or retro-fitted), do not have traction control/vehicle stability control fitted...

Hmmm. I've got an old car with both cruise-control and traction control fitted as standard. But I'm only a bollix.

I once aquaplaned (front wheels lost traction) on my previous 9-5 when cruise control was engaged. The CC switched itself off immediately when wheelspin was detected. The car had traction control (TCS) but not stability control (ESC).

Explanation: The Trionic engine management ECU on 9-5 relies on ABS/TCS ECU for speed signal and they share the same CAN bus. When the TCS detects wheelspin (at least one front speed sensor registers higher speed than rears while brakes are not applied) it sends a message to engine management to reduce throttle. I'm guessing that the latter then switches off the CC, which is built in functionality in Trionic, as a safety measure.

keithclancy

Happened to me too .. Cruise Control just turned off.

jimgoose

keithclancy wrote: »

Happened to me too .. Cruise Control just turned off.

Yeah, that's what I would expect from a vaguely modern set-up.

galwaytt

OSI wrote: »

If anything, the cruise control will ease off the accelerator. When your tyres lose traction, they speed up and as the CC takes it's speed from the wheels, it would think the car was going faster than the set speed and ease off the accelerator.

I would have thought it the other way round, tbh. Aquaplaning is where the rotational speed of the wheel is lower than the actual speed. In that scenario, simplistically at least, the car will apply power to try and increase it's speed........and yet never get there !! :eek:

Of course this is all complicated by figuring out how does it know what speed to do if say it's measuring (as distinct from driving..) wheels are all out to lunch ?? It's all very chicken-and-egg, and complicated further by issues of fwd/rwd/awd.

Throw in traction control, ESC etc and it's all very ........er..........complicated !