ABS and Audi's "Antilock Off" Switch

[Mark Rosenkrantz]

I've been instructing for Audi at winter driving schools since 1999 or
2000.  ABS engagement IS wheel lock-up.  Threshold ABS usually can shorten
pure ABS stopping distances.  For most drivers without significant training
(and yes, I include enthusiasts and people with some track days) on snow,
full ABS is the way to go, especially on newer cars.  Pre-2000 (1980's and
1990's vintage) the ABS was pretty bad.  Better than not having it, but
newer systems are quite good.

Here's the scoop:

1.  There is one (and only one) condition where disabling ABS (allowing the
wheels to fully lock up) will shorten the distance.  That is with a
slippery substrate (bottom surface), such as ice, with snow on top.  A
locked-up tire in these conditions will act as a "plow" and build up snow
in front of the tire, shortening the distance.  You give up all ability to
steer, however.

2.  Don't confuse disabling ABS with disabling ASR (anti-slip regulation
which controls wheelspin) or anti-skid control (those squiggly lines on the
icon).  Those are integrated and I could add into the discussion if some
desire.

3.  If a wheel is locked up, you can't turn.  You must control, IN ORDER:
A.  Wheelspin/wheel lock up
B. Understeer
C. Oversteer
D. Counterskid (from oversteer correction)


I can't stress enough that the newer the car, the better these systems
are.  For almost every single driver and situation, it IS better to leave
these systems engaged.  There are a few exceptions, and then only for
formally trained drivers READY to react instantaneously.  I keep my systems
engaged on the street.

Hope I've helped!!!!
Mark Rosenkrantz

On Thu, Jan 31, 2013 at 10:13 PM, mboucher70 hotmail.com <
mboucher70 at hotmail.com> wrote:

> In December, during a highway drive from Toronto to Montreal, weather
> turned quite bad.  At some point we were brought to stop-and-go traffic,
> perhaps between 0 and 20 km/h.  At one point when we needed to stop, it
> turned out that we were on black ice hidden by blowing snow.  The ABS
> kicked in, and it seemed as though we’d sail straight into the car in front
> of us!  I kept solid pressure on the pedal, and we JUST managed to stop,
> probably within a few inches of the car in front.  If we hadn't stopped, it
> wouldn't have been much more than a harsh bump.  Nonetheless, it’s a bad
> feeling!
>
> I'd had similar (though not nearly as bad) experiences in the past, but
> still never disengaged the ABS because all of the studies I'd read had made
> the case that ABS could save your life if you locked up the tires at high
> speed.
>
> After this near miss, I’d had it with the ABS.  I immediately put the car
> in park, pressed the "Antilock Off" switch, and continued the drive.  It
> felt so much more in control, at low speeds, even if I was locking them up
> at times.
>
> Question I've been pondering is what's to be concluded from this about the
> "Antilock Off" feature that used to be available:
>
> 1.) It was useful in situations such as that above, but since the overall
> benefits of ABS outweighed the downsides, it just became a standard safety
> feature and “Antilock Off" switches disappeared.
>
> 2.) ABS has significantly improved from designs used around the 1990
> vintage, to make the need to disable them obsolete.
>
> 3.) The “Antilock Off” switch was a useful feature and would be nice to
> have in current-day production cars.
>
> Other thoughts?
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