From: sml@plato.ds.boeing.com (Stuart Lewis)
Subject: Re: Weather on I-5? (skid control)
Summary: rebutting some statements regarding snow driving (long)
Keywords: driving technique - regardless of vehicle
Organization: Boeing Defense & Space Group
Date: Fri, 18 Dec 1992 02:49:13 GMT

In article <MS-C.724567097.662824084.mrc@Ikkoku-Kan.Panda.COM> Mark Crispin <mrc@Ikkoku-Kan.Panda.COM> writes:
>Laura Halliday suggests backing off on the power to recover from a skid in a
>rear drive car.

[sounded like Laura has done it once or twice]

>Not good, unless your skid is in an American Piece of Junk (APoJ) that tends
>towards understeering.  Backing off on the power in an oversteering skid will
>cause more weight transfer to the front of the car, which is exactly what you
>don't want.

First, Mark, skid control and recovery has nothing to do with what
type of vehicle one operates.  It's the operator.  I'll match my
winter driving skills in any of the my three, "American Pieces of
Junk" as you say, against you in your "*** Crap" any day. That
includes my 4500# '72 Impala.  When I still had Wyoming plates, I
had a *jeep* that had given up trying to navigate a hill, decide 
to get off the shoulder and follow me after I had managed
to weave around and through all the abandoned cars and plunge on.  If
the above method is how you try and control your vehicle in the snow,
I'll wave to you in the ditch next time I go by - nothing personal.
Now that I have that off my chest.....

Backing off the gas is *exactly* what you do with rear wheel drive -
keeping on the gas *will* make the skid worse.  You may end up
doing a 360 if you don't back off - studs or no.  If your back end
breaks loose and swings right, that's the direction you steer.  You
need to put the tread of the tire pointed into the direction that it
functions in.  Once done, gently steer back out of the skid.  If you
just keep steering left, the front tires are going to be
perpendicular to the direction they normally get bite from.  That's
a big help.

With our recent (last night) snow, I had opportunity to apply these
laws when I hit some black ice on the Green Valley Road out of
Auburn (very windy, very curvey, very icey - 1 a.m. last night).
I saw, this a.m., the results of two others who weren't so lucky -
one in the exact same spot I slid.  He/she had sheared off a phone
pole and ended up nose down in the ditch.  That immediately tells me
that dumb sucker was going too damn fast if they did that much damage.
When driving in snow, the object is to get there.  Not get there first.
Stupid, stupid, stupid.  Oh yeah, it was a front wheel drive car.
The other person hit black ice on a curve and his tracks went
straight-as-an-arrow off the road, body sideways - just as he was in
the skid, and into a ~42" diameter log that the farmer put there to
keep idiots like this from going through his fence.  Guess which way
his tires were pointing?  Yup, *away* from the skid.  People must
think that you just steer where you want to go - ice or no ice -
and, by darn, you should be able to go there!  From the looks
of his windshield, he/she did a nice face plant into the glass.
Dumb sucker number 2 - not wearing a seat belt in *especially*
hazardous conditions (not that one shouldn't anyway).

>First, some definitions:
>
>The ``contact patch'' of a wheel is that area of the tire which is in physical
.....
>``Adhesion'' is the tendency for the contact patch to adhere to the surface of
......
>The ``limit of adhesion'' is that point where the forces operating on the
.......
>``Understeer'' is the condition which occurs when a vehicle, brought beyond
........
>``Oversteer'' is the condition which occurs when a vehicle, brought beyond the
.........

[Jeez...  I must be to simplistic in explaining the technique! :-)]

>Icy conditions are quite suitable for oversteering.  The general scenario is
>that the driver applies too much braking, causing weight to transfer to the
>front wheels.  The rear wheels, suddenly without much weight, lose adhesion
>and the car responds only to the front wheels.  The typical reaction of an
>inexperienced driver is to overcompensate in his steering and hit the brakes;
>this takes even more weight off the back end, and the car swings around in an
>even more violent oversteering skid in the opposite direction from the
>original skid.....

Well stated.

>The right thing to do in an oversteering situation is to apply enough steering
>to straighten the car out, KEEP OFF THE BRAKES, and wait until you are pointed
>in the direction you want to go, with your rear wheels behind your front
>wheels.  Then, PUNCH the throttle -- this will cause a sudden transfer of
>weight to the rear wheels, which will dig in and your car will happily go
>where you want it to go.

Poorly stated.  You, "PUNCH the throttle" and you're right back in
it!  You're on snow/slush/ice - what are you going to "dig in"to?
"PUNCH"ing it is going to put you back into a fishtail - going in
the opposite direction of the original skid.  Never,
NEVER, *NEVER* do anything to the throttle and brakes other than
what I said in my original post: "light on the gas, light on the
brakes".  We're not taking laps out on the track at SIR in August.
Never do anything sudden or abrupt - in gas, brakes or
steering when driving in snow.  I've got one hell of a lot of miles
on snow and ice.  I'll stand by what works in practice, rather than
what sounds good in theory. [again, front wheel drive reacts
differently, but you still want to pretty conservative with the
throttle]  You are right on target with the first sentence.  But
simply resume *normal* throttle pressure with the "steer-out"

>If you are not pointed in the direction you want to go, the fastest way to get
>there is to let off the throttle.  The less power you apply to the rear
>wheels, the faster your turn will be.  Try to keep your steering wheel steady;
>in a skid your throttle is what you use to control your turn.

It seems you're contradicting yourself - let off throttle to regains
steering [correct].......use the throttle to control the turn [not].
Steering controls your turn, throttle propels you.

>Whatever you do, keep off the brakes.  If your car is in motion, the only hope
>you have of regaining adhesion is if your wheels are also in motion.  You will
>regain adhesion when the motion of your wheels match that of the car.  If you
>lock your wheels -- which you will do if you hit the brakes in a skid, you
>have lost all hope of regaining adhesion.

Yes, yes, yes.  And the only way to get your tires "in motion" is to
steer them in the direction you're traveling.  If you're traveling
east, and steering north, your tires aren't going to be rolling too
well - and that means they are no help to you.  Get them spinning,
at speed, in the direction of travel, then put them back to work for
you.  And too, I just realized that in all this
conversation, the single most useful tool (next to good tires and
driving smart) for snow control is, use your transmission.  It
doesn't matter if it's automatic or manual.  When approaching a
curve that you need to slow for, downshift - you *will* need to
compensate in your throttle by running the rpms up so that tire speed
remains constant - *don't* let the tranny grab and slow your drive
tires all in one lurch. Give a little gas on the downshift and when
the shift is complete, then back off and let the tranny slow you
down gradually.  You should be able to drive the windiest roads for
miles and never use your brakes once.  (You really should use both,
in tandem, with each other, but I'm just making a point)

Same thing for going down hills - downshift at the crest and let the
transmission keep you back.  Going up hills, shift down ahead of
time - at the base.  Don't get halfway up and let your automatic
drop a gear on you - good way to brake the rear loose [rear wheel
drive only]  For a manual, you don't want to release the drive to
the wheels even for an instant - once you've got momentum and
traction, you don't want to loose it.  Actually, for a front wheel
drive, you don't want to break the front loose either - once you
loose traction and spin, you may not get it back.  (picture in this
a.m.'s Valley Daily News of a guy sitting on the right fender ("over
the drive wheels", caption stated (front wheel drive, obviously)),
while his wife was at the wheel trying, unsuccessfully, to get in
the couples driveway).

This is sort of going on and on - a lot longer than I sure intended.
Sorry.  The season is young; we're sure to get more snow before it's
all over.  Keep your tires inflated, throw some sand in the trunk,
light on the gas, light on the brakes.  If you have 4-wheel drive,
don't use it as a cruch thinking it will go anywhere for you - there
is no substitute for good driving skills.  Give yourself plenty of
time.  Like I stated earlier, the object is to get there, not get
there fast.  Snide comments aside, I feel real bad for the person
who left an imprint of their face in the windshield of their Ram
D-50 this morning.  I was in an accident in which my front seat
passenger did this.  Pretty ugly.  It's just not worth it.

Sorry, Mark, if I got a little inflamed.  Like I stated in my
original post, you have to use common sense in the snow, and some of
the techniques you cite will get you in trouble.  Don't take my word
for it - ask any net.transplants who are from real snow country (Montana,
the Dakotas, Nebraska, Wyoming (me)) how they drive.  Like the great
musical sage Jimmy Buffet would say, "Don't try to describe the
scenery if you've never seen it.  Don't ever forget that you just may
wind up being wrong...."

Stuart Lewis
sml@plato.ds.boeing.com
Newsgroups: pnw.general