if ABS isn't helping it's either a very
poor implementation or you are using the incorrect tyres for the
conditions
ABS is all about keeping the wheel rotating and preventing spinning - the
highest coefficient is at impending skid.
At low speeds if a vehicle with ABS is being braked on unpacked snow, like
in a parking lot, it will stop faster if the tire is allowed to build up a
snow wedge in front of itself, as in sliding with no rotation. With ABS
active, the tire will try to roll over the snow, not allow the tire to slide
and not build up the wedge.
I've heard this from several suppliers of ABS over the years.
This scenario was related to me as being common in Europe and was the reason
Audi (back then at least)went with the switchable ABS system.
We (the US) didn't believe the driver was smart enough to know when to turn
it off and felt it would have legal implications. Don't know if it (on/off
switch ABS) is still being done on any vehicles.
Kenneth Waller
----- Original Message -----
From: "Rob Studdert" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Sunday, October 23, 2005 6:44 PM
Subject: Re: Self Portrait?
On 23 Oct 2005 at 16:43, Kenneth Waller wrote:
> I would like to be able to turn off my ABS though
Audi used to have a shut off switch in their European models. It
presupposes
that the operator is smart enough to know when to shut it off (like in
unpacked
snow).
Most vehicles with traction./stability control allow it to be overridden
however I don't know of any ABS enabled vehicle that allows ABS to be
actively
disabled. Of course the vehicle will disabled ABS if it fails to pass
tests
after the vehicle is started but really if ABS isn't helping it's either a
very
poor implementation or you are using the incorrect tyres for the
conditions.
I had an old '89 Volvo 740 Wagon (don't comment, it was a good wagon),
it's ABS
implementation was pretty early and it definitely had some strange little
quirks. There was one hill terminating in traffic lights that it regularly
had
a problem with. Right at the bottom of the lights was a small
depress/pot-hole
and if the wheel caught it whilst coming down the hill often I'd find
myself
easing into the intersection courtesy of the ABS, not fun. I suspect that
the
rudimentary wheel rotation sensor systems are a far cry from the current
implementations which employ accelerometers and yaw, pitch sensors.
Rob Studdert
HURSTVILLE AUSTRALIA
Tel +61-2-9554-4110
UTC(GMT) +10 Hours
[EMAIL PROTECTED]
http://members.ozemail.com.au/~distudio/publications/
Pentax user since 1986, PDMLer since 1998
