ABS and Audi's "Antilock Off" Switch

[mboucher70 hotmail.com]

Thanks all for the detailed answers and thoughts.  

As usual, details are everything, so when I wrote ‘black ice with blowing snow’, actually, the snow was not only blowing, it was accumulating faster than they could plow it.  So that’s what I was really lamenting: once I had disengaged the ABS, I felt a lot more in control by having the option to lock up the tires and gaining the snow-plow effect.  Totally realizing that this loses the ability to steer, I’m really referring to stopping from a 10-20km/h speed in a straight line.

And in terms of the newer the car, the better the ABS design, that would also help explain.  Mine is 1990, so I guess most cars on the road these days have more sophisticated ABS systems.

Best,
MC

 

From: Mark Rosenkrantz 
Sent: Friday, February 01, 2013 5:40 PM
To: mboucher70 hotmail.com 
Cc: quattro at audifans.com 
Subject: Re: ABS and Audi's "Antilock Off" Switch

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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