Mole wrote:
Interesting. First of all, you needn't worry about it running out of puff. The pump keeps making more as required. It uses a fair amount of power too. When the ABS pump kicks in on my wife's car, I can see the headlights dim momentarily!
On earlier generation ABS cars, the kick-back pressure was built up with an electric pump, but the rate of replenishment did not match that of continuous use (I think it held about fifteen kick-backs from memory, then took a minute or two to build back up). You're likely right though that these days they're wise to that.
Mole wrote:
I'm sure all cars will be subtly different in how they decide to cope with extremely low friction surfaces. Yes, the film of water will build up in front of a locked wheel, but I sometimes wonder whether the simple fact that the wheel is repeatedly rotating and locking (even with no grip at all) still means that some energy is being taken from the moving car and turned into something else. The bottom line is that I simply don't know enough about it to be sure.
Nor me - though the calculational processes in parallel in my brain were doing their damndest to work out the best course.
Mole wrote:
Conventional wisdom says that virgin snow is one of the few situations where the locked wheel will stop QUICKER (because of the wedge of snow that builds up in front of the tyre).
definitely.
Mole wrote:
There's also the possibility that the ABS doesn't work below certain speeds (some cars don't) and you were below that speed. The intervention that you felt might simply have been the ESC trying to keep it pointing the right way rather than the ABS trying to stop it.
That'#s also possible - and one aspect I'd not considered. However, I *was* getting pedal kick-bak. I think (but am not sure) that ABS takes priority over ESC - when the brake pedal is touched.
Mole]Too many unknowns really, but glad you're here to tell the tale - must have been a pretty trouser-browning moment![/quote]
[quote="Mole wrote:
Incidentally, whilst generally hugely impressed with Mrs. M's Nissan X-Trail, I had a bit of a "moment" myself the other day. I passed a van on a fairly steep snowy hill and he wasn't going anywhere. Being a decent chap, I thought I'd stop and help. I stopped some way in front of him, applied the handbrake, and went to get out, but as soon as I took my foot off the footbrake, it started sliding back down towards the van with it's back wheels locked! I got back in (pretty sharp-ish!) and re-applied the footbake - whereupon it stopped. Now the dilema! It was fine if left in gear or with my foot on the footbrake. Being a 4x4, it has sufficient traction to climb slippy slopes that it's own handbrake then can't hold it on! Obviously, if it was a "proper" 4x4, it would have a transmission handbrake that worked on all 4 wheels. Needless to say, I wasn't in a position to offer him a tow, and even setting off again myself was a bit tricky!
I have to confess the only time I came acrosss someone coming back at me (trying to go forward) on an uphill stretch, I went past it and kept going. That was years ago.