Never Use Cruise Control When it's Wet?

[jamesh764]

Cruise control works out your speed from the speed sensor in the gearbox - i.e it counts the revolutions of the output shaft of the gearbox. If the wheels were spinning then the driveshafts would be turning faster than the car was moving so if anything then surely cruise control would reduce throttle rather than increase it.

I've used cruise control in the rain and I am not dead yet.

[matpilch]

most cars that are fitted with cruise control also have traction control on board and that will cure any symptoms of wheel spin

[alangla]

My last Focus had cruise control but no traction control (yes, I was too tight for the £250 option, didn't seem worth it on a 136hp TD with fat tyres), I'm pretty sure when it hit serious standing water with cruise on it either kept going or, in the more extreme cases disconnected the cruise control & shut the throttle. What the other posters said about cruise control basically counting wheel revolutions at the gearbox & checking they're within parameters sounds right - the sudden increase in wheel rotations when the car lost traction would probably be enough to create an error in the ECU & cause it to fail safe by disconnecting the CC.

[AC43]

pherlopolus said:

McWigglebum4th said:

Mmmmmm

If a car was driven onto sheet ice and the cruise control set at 30mph while chained to a large post



how fast would the wheels be spinning?

How fast would the car be traveling?

Will it take off if it's on a conveyor belt?

If it's a diesel yes; because of all the torques.

[Mound Dawg]

matpilch said:

most cars that are fitted with cruise control also have traction control on board and that will cure any symptoms of wheel spin

Mine doesn't have traction control but it does have a throbbing great 68 bhp 1.2 engine which is pretty much the same thing.

[Phil Dicky]

Gonewest said:

Is it also true that if you own a Winnibego, or similar, motorhome you cannot get up out of the drivers seat to make a coffee whilst being on cruise?

According to Anchorman 2 you can.

[J4CKO]

Are these the same people that post that Gypsies are going round marking houses where the owners have a dog so they can later come and steal it ?

[ModernAndy]

Debaser said:

OP, don't worry about it. If conditions are bad enough that you think aquaplaning is likely, use common sense.

Indeed and that is the approach I always drive with, I would never ever, ever set cruise control to a daft speed for the conditions.

I'm not so much asking about correct driving techniques as much as I'm interested in if cruise control can be flummoxed by road conditions though. I am also aware that the car isn't going to break physics and take off, I'm just wondering is it possible to cause a loss of control by using cruise when conditions are really bad.

[ModernAndy]

J4CKO said:

Are these the same people that post that Gypsies are going round marking houses where the owners have a dog so they can later come and steal it ?

Probably, it definitely was one of those types of posts. It did mention the car 'taking off' but I didn't take that too literally, I just thought they were exaggerating a skid of some variety.

[pherlopolus]

I actually posted a 'before anyone says anything, yes you can use CC in the wet' on facebook, had an elderly relative in australia pipe up that they had a senior motor tech on the radio telling people to not use it :S

[sploosh]

My Saab 95 doesn't have TC. I've aquaplaned a few times on cruise, revs drop and car slows down then suddenly speeds up when you get out of the puddle, which is where the problem would occur. I make a point of turning cruise off when it is really wet.

[M11 MFP]

Certainly in the 90's & 00's some American trucks had a warning in the manual and cab about using cruise control on frozen roads. I would assume the system combines with traction control or slip measurement now to prevent this happening.

[DaveCWK]

This was indeed an issue with early/less sophisticated systems and I think was to do with the speed which they reacted. Hit standing water in a rwd car, car slows down instantly by 3 to 5mph, cruise applies more throttle to rear wheels, you can see what might happen. Mondern stuff which is integrated with traction control, ESP etc it's not an issue.

[dvs_dave]

I remember being with my dad back in the 90's in his S class in heavy rain with the cruise on, and due to aqua planing the rear wheels started to momentarily spin up due to the sudden loss of traction before the TC kicked in to sort it out. Took a couple of times to realise the cause was not a malfunction, and we needed to slow down.

[dvs_dave]

jamesh764 said:

Cruise control works out your speed from the speed sensor in the gearbox - i.e it counts the revolutions of the output shaft of the gearbox. If the wheels were spinning then the driveshafts would be turning faster than the car was moving so if anything then surely cruise control would reduce throttle rather than increase it.

I've used cruise control in the rain and I am not dead yet.

Most cars these days use the ABS/ESC module for the speed signal rather than the gearbox output. Gearbox output speed doesn't necessarily reflect actual road or wheel speeds.

[wiliferus]

LeoZwalf said:

McWigglebum4th said:

Mmmmmm

If a car was driven onto sheet ice and the cruise control set at 30mph while chained to a large post



how fast would the wheels be spinning?

How fast would the car be traveling?

mmmmmm can we add a conveyor belt into your equation? ;-)

We need more info.

Are the back seats folded down or not?

[anonymous-user]

er, i think people are perhaps thinking that cruise control just slams open (or shut) the throttle in response to minor variations in measured (not necessarily true) roadspeed! Well, sorry, but it doesn't. OEMs have a massive raft of CC calibration methodology and attribute calibration, which are precisely developed to prevent the CC system causing safety, comfort, or durability issues. As such, on modern systems, the cruise control is considerably more subtle than most drivers when it comes to throttle inputs (actually, torque demands to the ecu, it doesn't control the throttle angle directly, unlike old systems). People like me spend weeks & months skidding around places like Northern Sweden, Arizona, High in the Alps or pounding round endless test facilities to ensure that your car is safe under all conditions.


So, if road conditions are bad enough to result in a loss of control of your car, the cruise control is the least of your worries!

[4lf4-155]

andy-xr said:

I had mine on driving up the M74 last year through snow. Couple of places it went a bit wonky but the traction control sorted it out. Didnt drop off cruise

This happened to me too, although the cruise control disengaged on mine.

On balance it seems sensible for the power to disengage after a traction control event.

[Jader1973]

pherlopolus said:

I actually posted a 'before anyone says anything, yes you can use CC in the wet' on facebook, had an elderly relative in australia pipe up that they had a senior motor tech on the radio telling people to not use it :S

Australians are completely incapable of driving in the rain though. Slightest hint of dampness and they lose what little driving ability they have.

[wiliferus]

Jader1973 said:

pherlopolus said:

I actually posted a 'before anyone says anything, yes you can use CC in the wet' on facebook, had an elderly relative in australia pipe up that they had a senior motor tech on the radio telling people to not use it :S

Australians are completely incapable of driving in the rain though. Slightest hint of dampness and they lose what little driving ability they have.

I lived in Australia for 6 months with my then girlfriends family. I remember saying I was popping to the shop during a moderate rain shower. By the look on their faces you'd have thought I was going out during a meteor shower. They firmly believed the car would just fall off the road because it was wet.
Their approach to driving in rain was comparable to ours for snow.