Winter braking technique - Quattro diff locked.
Suffolk GameServer LAN
suffolk.associates at verizon.net
Thu Dec 5 01:22:08 EST 2002
I'm gonna go out here only for a BTDT.
Not to start a Torsen like thread about the pros and cons, but(s) and if(s).
While I'm not the authority by any means I'm pretty good at what I do, even
though I still have a lot to learn.
In snow and ice: (pre ABS) like a 4000Q.
Locking the diffs gives a neat straight line effective "engine breaking
effect" distributed better to all four wheels VS. brake pedal modulation
using the the brakes alone to prevent wheel lockup. Its kinda is like a
crude primitive ABS which can be overpowered by firm brake application to
lock the wheels - and stall the motor.
However, the "crab walking" effect once one starts to turn/corner on snow
/ice is quite uneasy and not very effective anymore.
In the past in absence of traffic,
I could drag the brake pedal to see which wheel would lock up (for a sign of
lost traction - like an icy road/black ice) then the engine would over come
the light braking torque by forcing that wheel to spin again.
Good senses would pick up which wheel was skidding/locked up/lost traction.
The speedo would drop from say 50 to 30 and then back up to 45 as a visual
Generally, this would cause me to slow down and keep me out of some
I liked the option in my old 10V 1990 200 TQAvant to turn off the ABS,
ONLY in 2% of all situations. Why?
Well in (for arguments sake) straight line braking,
(snow pack and gravel only - no ice -) the car could be stopped in a shorter
if the ABS was off.
In that specific situation: I could trap a wedge of material like snow pack
or gravel in front
of the (surface area) of the wheel(s) to cause the additional drag (higher
coefficient of friction?) to come to a stop in a shorter distance than with
ABS allowed the wheel(s) to rotate and run over the material under tire so
the plowing of material against the wheels was not present.
This (ABS off) tactic would do nothing for steering input or ability as
straight line physics of momentum would be in play.
However, I could "drop" a wheel into the shoulder of the road in a turn and
by having that dropped wheel slowed down by the force of plowing through the
snow pack/gravel I could pivot or rotate the car around that wheel, in the
corner, if I was going too fast to make it around the curve.
I would however, strongly discourage just "Trying it".
It is my opinion that most SUV's off the road are due to heavier, high
center of gravity vehicles
driven by inexperienced drivers going far too fast for the conditions.
Then throw in the lack of "snow" tires on them and I'd say each travel trip
just got much more scenic.
Scenic = Trucks and SUV upside-down or into guardrails.
The threshold of "loosing it" in identical vehicles IME (in 2wd vs 4wd/awd -
like 4000/4000Q and trucks) is generally raised to the point that if you do
loose it going faster in 4wd/awd, its extremely harder to get the vehicle
back down into control. Losing traction/handling a 4000 fwd in snow/ice @
35 MPH was much easier to recover than a 4000Q awd losing it @ 50 MPH which
was a handful.. Physics looked at each as roughly the same weight.
IME Front wheel drive in a 4000 is ONE wheel drive. Just like a 2wd truck,
one wheel spins (unless you opt for positraction.)
Having - specifically - snow tires (or ice compunds) was a major advantage
regardless of 2wd or 4wd/awd.
The below quote is so very true about the braking of any vehicle.
Quattro makes you Go................not stop better.
-Scott in BOSTON
>One common mistake people new to quattro/AWD make
>is to assume that, since you go better in snow,
>you stop better in snow. But the reality is that
>you have 4 wheel brakes just like every other car
>on the road -- you're not going to stop any better
>because of the 4 wheel drive.
>If you drive a lot in the snow, you may notice
>an above average number of SUVs off the road and
>into the weeds because bad assumption.
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