ABS

[Darrell Norquay]

At 09:40 AM 1/30/97 -0600, John Hess wrote:

>And it is this slow speed turnoff that allows so many people to skid 
>(literally) hundreds of yards on ice.  How far do you think you can 
>skid with the wheels locked versus reasonable application of the 
>brakes on ice.  For myself (perhaps not everyone), I find it easier to 
>try to keep from skidding in the first place on ice and to maintain 
>some control over which end of the car hits (or, perhaps misses) the 
>tree.  One has no chance of doing  this even at VERY slow speeds 
>unless the wheels are turning!

Under zero traction conditions like sheer ice, ain't nothin gonna stop you,
ABS or no.  The miniscule coefficient of friction between rubber and
polished ice is all you got (and mebbe some air drag), no matter if the
brakes are locked, pumped, ABS'ed or off.  No way ABS will *decrease*
stopping distance under these conditions, but it probably won't *increase*
them appreciably either.  The only advantage of ABS in this situation is
that you retain some semblance of directional control, which you *do not*
have with locked wheels. The whole point of ABS is not to make you stop
faster (it doesn't) but to retain steering control (it does).

And GMD wrote:

>I can see independent 4 wheel braking as the way to go for maximum traction.
>Chevy trucks have the rear wheel only ABS that works off of the tranny VSS,
>I think. As we all know, most of the braking is at the front wheels. What's
>up with that?

Since pickup trucks are generally light in the tail unloaded, they tend to
lock up the back wheels first, throwing you into a skid.  Rear only ABS is
meant to handle this condition.  I had a 91 Dodge Dakota, and the rear ABS
sensor was in the differential, and sensed the teeth on the ring gear.

And Andrew Rabbit wrote:

>The worst thing I found with ABS on ice and snow was that it kept on
>working!  I reckon at the speeds you travel at when on ice, a good driver
>can modulate the brakes as good as an ABS system, AND gets the choice as to
>whether to lock the wheels or not.

Yeah, we have ABS on several of our newer vehicles at work, and it scares
the hell out of me.  Nothing worse than tromping on the brakes, hearing that
hideous groan of the ABS modulator, and keeping right on going.  It does
help control a skid better, but if you are accustomed to driving in these
conditions as I am, you won't get into the skid in the first place.  IMHO,
I'd much rather be following a good, experienced driver with standard brakes
than an inexperienced driver relying on ABS to keep him out of trouble
anyday.  ABS has it's place in conditions where you are not expecting
traction problems, where it works well, but on ice it is both unnecessary
and unnerving.

regards
dn
dnorquay at iul-ccs.com