Driving on snow / quattro system

[gfl@cc.bellcore.com (grant f lenahan)]

Ah, lots of misinformation flying around, that's what the
internet is good for . . . 

1) The quattro system cannot be "turned off".  It is
a set of permanently engaged differentials, front, rear and
center.  On older models, the rear and center diffs could be 
"locked" (no diff action any longer) for better traction still.

All-wheel drive does improve cornering on snow somewhat,m
but face it, all cars have four wheels to corner on.  The
improvement comes from "balance" in how traction is applied and
because neither the front nor rear wheels are close to spinning.
Once they spin, all (most) traction is lost.

Beyond snow cornering, the "q" system is very good to
improve handling on dry and wet roads.  Again, you gain
the more natural balance of rear-wheel-drive without
the same degree of tail-happiness (like a BMW).  On wet
roads, a Q will accelerate through a turn in a way that
would cause a similar FWD car to plow (run wide) or a RWD
car to fishtail.

On later Qs, the center diff is no longer lockable.  It is
a "torsen" (TORque-SENsing) diff, which allocates torque
to the end with the most traction, to a maximum split of
25%/75% or 75/25.  It cannot be mechanically locked.

Grant