Makes sense to me due to the threat of hydroplaning. My van hydroplanes at 40 MPH in heavy rain.
I know for a fact that you do not want to use it if their is a chance of snow or ice. The vehicle wants to go the set speed, if it hits ice, the motor goes up trying to maintain that speed.
Probably the same thing with wet roads. Traction rules.
With the traction and stability control in the newest cars, probably not an issue, but as mentioned you can end up with wheel spin in older cars, and that’s not good...
I don’t use CC on wet or snowy/icy surfaces. JMO.
Excellent question!
There are many “barban” or nizal settings on the cruise control potentiometer, and because the solenoids and senders are internal, the accuracy of these settings is a question both of interior and exterior moisture or wetness.
As an aside, the brothers who invented auto AC and Cruise Control (Hiram, Lowrance and Max Bingham) debated without end on this subject with Lowrance and Hiram insisting despite all evidence that water content or droplets in the air made no difference whatsoever.
Now, thankfully, it is generally believed by experts that a minimum of humidity is critical for the proper functioning of cruise control, and that you should bypass both Lo and Hi and set your A/C all the way to Max.
My opinion:
Wet road: Okay.
Icy road: A bad idea with rear-wheel drive. Okay with front-wheel drive.
I don’t know where people get the idea that the engine will rev unsafely on ice. If the speed is set at, say, 40, the engine is going to turn the wheels at a speed that corresponds to 40, even if the car is going a bit slower than 40.
I use cruise control a lot, even on icy roads. I installed my first cruise control on a new 1973 Chevy van, and have used it ever since. I don't recall that it has ever inadvertently spun a tire on wet roads. It has spun a tire on icy roads possibly once or twice, and I lived where there were a LOT of icy roads.
Its not a good idea.
Yes, because if you hydroplane, you have to tap the brakes (or would instinctively) and that would make it way worse.
I have a vehicle with a dynamic cruise control system, where it follows the vehicle in front of you, up to the speed you set it. If you have the wipers on (beyond intermittent), the dynamic part of the cruise control will shut off. But you then revert to a conventional system and can drive all day on it.
This tells me that, at least, the manufacturer was not concerned about using a cruise control in the rain - and I agree. I’ve had cruise controls longer than I’ve had cars (and I’ve had cars for decades - my first cruise control sat in a box waiting for me to get my first car).
I never had ANY of the problems that people claim (sleepiness, control, etc.). I’ve never had a cruise control do a burnout on wet pavement, ever. They simply don’t gun the engine to that level. On ice, as long as you’re up to your speed, it’s no different than using the throttle - and I’ve done that many, many, times.
So just ignore the IDIOT advice. It’s safer to be looking out your windshield when driving than to have to keep looking at your speedometer.
The speed is measured by the rotational speed of the transmission including the gear currently in use, not movement of the car versus the road by some magical sensor or gps.
If your tires slip on any slippery surface, snow, ice, wet, etc, the tires and the drive train initially speed up, even though the vehicle itself hasn’t accelerated in forward motion. So the cruise control would actually try to slow down, not speed up.
If they added some kind of mechanical speed sensor at a tire that was not a drive tire, like used on a bicycle, it would do the opposite, sensing that tire slowing down and try to speed up the slipping drive wheel.
I can think of no functional constraints with today's cars - it's all human-oriented as far as the pros/cons.
It happened to me once in heavy rain on cruise control scared the crap out of me when my steering went away. Kicked off CC as soon as it happened.
Just don’t go to the back and get a cup of coffee.
I have hydroplaned while on cruise control. One unintended lane change was all it took for me to never do it again. I like being able to immediately let off the accelerator when the tires start breaking loose.
I woul dnot use it in wet weather. Every once in a while, my car hydroplanes...even at relatively slow speed, when some imperfection in the road makes the water deeper.
The instinct is to let off the gas..and all is well. With cruise on, I think the ‘reaction time’ of the control will be too slow.
With cruise control set you can become inattentive. Better to have your foot on the gas and your mind alert to changing conditions.
There are different cruise controls out there. Some are smarter than others. Even if some have conquered the icy and wet roads problem, how do you know how smart yours is? You don’t.
Better safe than sorry.
One of the reasons you do not use Cruise on bad weather is you need 100% positive control of your vehicle and cruise does not do that for you.
I just got an email from State Farm the other day leading me to this link:
The relevant portion:
4. Turn off cruise control. Ironically, on rain- or snow-slick surfaces, cruise control may cause you to lose control. You might think it’ll help you stay at one steady speed, but if you hydroplane while you’re in cruise control, your car will actually go faster.