re: To lock or not to lock...

["Lawson, Dave" <dlawson@ball.com>]

Phil,
>I'm still agonizing about (and trying to learn from) what went wrong
when I
>put my '91 200q in a ditch and totalled it in December. Would your
>statement apply to recovery from oversteer with the '91 torsen setup?
Can
>you very _briefly_ paraphrase the UK Performance Car article? Thanks.

I remember your learning experience and I have tried to benefit from it,
by learning more about my torsen equiped 200q and how it handles. From
what I remember, you were rounding a corner at moderate speed, the road
was slick, the back end of  your 200 started comming around and then you
were upside down in a ditch. As I have probably said before, I had the
back end of my 200q wagon come around on me a few times this winter,
they were all at slow speeds, < 20mph, but it really suprised me.

This loss of traction happens because the forces on the contact patch of
the tire overcome the net friction available between the road surface
and the tire. This can happen because you are spinning the tires on a
slick surface (i.e.overcoming longitudinal friction) or sliding when
cornering (i.e.overcoming lateral friction). The levels of overcoming
the friction forces (also known as driving outside the friction circle)
depend on your two inputs, the tire and the road surface. The levels are
very high for a race tire on a dry track, the lowest level is probably a
race tire on ice. And we all drive some combination inbetween. Snow/ice
tires on ice increase the friction circle size compared to summer or all
season tires on ice. At steamboat I believe everyone is driving with a
snow/ice tire(non studded), but there might have been a few times people
have been there with all season tires. And it is a real eye opener what
the differences are. Snow tire equiped cars walk away from all the other
tires. (And quattros leave FWD cars way behind. BTDT) The point is, on a
car with all season tires, the level at which the tires loose their grip
is lower than a snow tire equiped car, so people should take that into
account.

I don't know the exact situation of your accident, tires, speed, road
conditions, etc., but what we learn at the steamboat school is
invaluable. During excercises, to get the rear of a car to break loose
and rotate, you abruptly let off the throttle, this weights the front
end, unweights the back end and the fun begins.  Throw in an off-camber,
downhill corner and it happens pretty quick. The recovery is to steer
into the skid and get back on the throttle. There are other steering
inputs, but you want the fronts to regain traction so you can complete
the turn, even with a wider radius. After playing in the 200 for a day
at steamboat, I feel much better about driving it. It is pretty easy to
break the rear end loose, but also easy to recover from small slides.
Big sideways slides take a bit more work but recovery is achievable.

You need to get out there and practice, find an empty parking lot on an
icy day or got to one of the winter driving schools. You will learn so
much about car control. Yes, it does cost a few hundred dollars, but it
is less than most peoples deductables when a car gets wrecked. 

Now for my most recent adventure... I took the family up skiing last
monday, driving my gmc safari awd(viscus center diff) and as we neared
idaho springs on I70, there was an explorer in the guard rail. I slowed
down a bit to maybe 50 and within a 1/4 mile I feel the back end of the
van start to come out. I slighty eased up on the gas, a slight steering
input, the tail came back in line with a slight oscillation and we
continued on. In the next 1/2 mile there were 2 other 4wd SUVs all
crunched up and fresh marks left from a few more that morning. It was
totally unexpected, and got the heart going for a moment. BTW, I am
guilty of running all seasons on my van, but after a few horrendous
winter drives this year, it is proably going to get some snow tires.

HTH.
-
Dave Lawson
93 safari awd
90 200q wagon
83 urq