Dave Tweed wrote:

> If you're in a situation with limited traction on all wheels (much more
> common), positraction gives you the ability to break loose a wheel that
> up to that point had traction -- especially lateral traction, as opposed
> to forward traction. In a turn, you'll spin out faster than you can react.

Speed vs. friction.  :-)

Got to see a bunch of this first-hand this weekend in the Colorado
mountains... people driving too fast for conditions.  Many of them in
fancy electronically-controlled 4WD vehicles.

I was trudging down the mountain from a remote radio site with a 2000
lb. trailer behind the Jeep Cherokee I drive, using 4WD Low with the
transmission in 3rd gear doing about 3000 RPM, just so I could get a
lower gear ratio to use engine braking to gently slow the whole works
down without applying the brakes when needed.

12 of the cars that passed me on the way down ended up in a pileup near
the edge of the foothills because they were simply travelling too fast
for conditions.

I just chuckled (after seeing that no one was hurt) as I crept on by in
the Jeep with the trailer on behind almost 1/2 hour behind them at the
bottom of the hill.

The only thing that really ultimately teaches winter driving is
experience and respect for the speeds and weights of vehicles on ice.
The guy in the Nissan Xterra 4X4 that had folded the front left axle
under the truck, and the Volvo AWD wagon that had most of the driver's
side door in the driver's lap appeared to be working on learning their
lessons the hard way.  :-)

This weekend was my first experience with a very low-traction road using
4WD at the same time as towing a trailer.  I'd prefer not to repeat it.
  Wasn't real fun, but slow and steady worked out okay (this time).
Probably more risky than I normally would care to attempt.

There were a couple of hair-raising moments when even gentle engine
braking would cause loss of traction to all four wheels and the trailer
would begin pushing the tow vehicle back-end to one side or the other --
  knowing when to slap that gearshift handle into Neutral and to
actually allow a slight gain in speed to coast and re-gain traction is
something only learned after years of snow/ice driving... and it assumes
that you've actually paid attention and tried hard to learn how your
particular vehicle reacts in extreme low-traction conditions.

In 15 years of Colorado driving I have never needed to put the chains
on, but I have them in the Jeep at all times during the winter...
they're a tool to get you to someplace warm and safe when you can't do
it safely any other way, and should never be used to get you out INTO
the elements... or at least that's what my grandfather taught me, and
it's a good way to view them.  Knowing the limitations of your vehicle
and staying within them is the only way to go.

Nate, nate@natetech.com

--
http://www.piclist.com hint: The list server can filter out subtopics
(like ads or off topics) for you. See http://www.piclist.com/#topics