ESP in a Straight Line

My understanding is it is the latter.

Look at this though

I am not sure that sudden change in rolling resistance alone is sufficient, but once the car deviates from the straight line the steering wheel points to, I would think the induced lateral acceleration should be large enough to have the system kick in.

- D.

Could have kicked in so seamlessly you just didn't notice it.... Or did you disable it with the dash button?

Sorry to hear about your mishap...life has a way of changing our plans doesn't it?

As for the ESP on the van, I am thinking it would kick in when the vehicle has either approached or exceeded its normal handling limits. As you say, emergency handling is a very different thing. Sitting way up high in a big shoebox and hitting the corners hard probably makes one feel they are closer to the edge than they really are. In other words, maybe I just wasn't pushing it hard enough to engage the ESP. I need to whip it around a parking lot when it snows and see what happens...first I need to clear out all my kids crap so it doesn't sound like a huge rattle when I toss it around a bit!

In the steering wheel, there is an angle sensor, and in the frame there is a yaw sensor. Technically, the values from both sensors should always equall each other. When there is a major deviation from the yaw sensor to the steering wheel angle sensor, the ESP starts braking individual wheels to have the vehicle pivot on it's axis.

- Peter

So my theory of little elves guiding me out of trouble is way off?

Last winter I tried this in my Passat GLX 4Motion with ESP. The car slid slightly, but I never saw the ESP dash light illuminate.

They're there...but they only work when ESP is turned off!

Yes, and you can read some details in the link I provided JD a couple of days ago. Of course it is a bit more complicated since the system has to compare acceleration (rate of change of direction), which depends on the speed. Also, the system does not know how good your traction is before it applies the corrective measures, so its feedback loop must be finely tuned, indeed.

From the diagrams you can see it makes the reasonable assumption that, because of static and dynamic load, the outside front wheel has the best traction and usually can be used as the main pivot point.

- D.