need_TQM

My take :

On a nose heavy car (or even equal weight) the front tires are asked to do more work in a steady state turn. They provide a force proportional to the weight balance, and also a little to continue the rotation in heading (90 deg turn, 180 deg turn, whatever).

Using a rear-biased torque split allows the rear tires which have to provide less cornering force than the fronts (lower weight on the rears and they don't provide the change in heading) to use their left-over traction to provide "go" force.

perdido34

I haven't found this to be true at all. If I go around a corner on a snow-covered street and just keep a steady foot on the gas, the rear end snaps into the proper direction almost immediately. I could only break the rear end lose if I were an incompetent winter driver and floored it in that situation. Whether the traction control or some other factor is responsible for this good behavior, I have no idea. I do know, however, that my last AWD car (2005 Saab 9-2x, essentially a rebadged Subie WRX) had no traction control and WOULD oversteer dramatically unless I lifted my foot from the accelerator as soon as the rear end started to skid.

a4Happy

That "snapping" of the rear end is for SURE the ESP helping you out. It hits the break on the front inside tire which makes the rear end snap right to where you want it, even if the road is a little slick. The problem though is that the B8 is doing this WAY MORE than what the B7 did, and this is not as enjoyable of an experience at higher corning speeds. If you take the ASR and ESP off (hold your ESP button down for 5 seconds) you'll notice that the rear end swings out more than you would have realized if not for the technology. I find myself turning off the ASR all the time as I can't stand how much it cuts the throttle in snow when going around corners. To bad it gets re-enabled when you turn the cruise control back on :-(

perdido34

When the snow stops, then I will experiment with higher cornering speeds<g>. About 10 mph was the right speed for today and yesterday.

kleinbus

Sounds like you have no winter tires huh?

perdido34

Correct--all season tires...

AvantMore

I just got my first winter set up ever, Blizzaks and wheels. Wholly molly, what a difference!!! Granted, I took off the P-Zero summers which were scarry with any snow, so the difference is exaggerated. ... Now I feel like I'm driving a Snow Cat. We got 8" the other night and I went out for some winter fun, found the steepest hills I could and climbed them all without any problem. (All seasons are still pretty good on the A6, but at least two steps below Blizzaks)

The ESP and all the other controls definitely kicked in a few times as I cornered - I left them all active to see what the electronics would do. I didn't like the feeling of 'loosing' control of what was going on, but they performed as advertised. Next chance in the snow, I'll figure out how to deactivate what I can and have some real fun.

Dirt

To further that though, in any 50/50 split car, when you reach the limit nine times out of ten you'll hit the front tires' limits first because the front tires have to both steer and provide motive force. Give that, you'd be at 100% capacity on the front tires and perhaps only 75% capacity on the rears. The effects of this are twofold. First, since fronts are at their limit the tendency will be under-steer and any attempt at throttle steering is likely to make the under-steer worse rather than better since we're not talking about drastically over-powered cars. Second, since you're already on the limit of the front tires the car's overall responsiveness will be sluggish because the front tires can no longer generate any additional side force to steer the car. Try to tighten your line or slow down a bit and the result will likely be more under-steer and you'll end up on a different line than you had hoped for.

Now, with a 40/60 split car, under the same scenario it's much more likely that both the front and the rear tires will be at their limits simultaneously. As such, the steering will be more responsive and the car as a whole will also be more responsive to steering and brake inputs. In theory, if a person knows what they're doing, the car will be more controllable at the limit because you retain a greater percentage of your steering capacity at the limit when compared to a 50/50 split car.

A third component to this is driving under the limit. Any power sent through the steered wheels will subjectively numb or affect the steering in some way, no matter how small the effect. The less motive force the front tires have to supply the better the subjective steering feel is likely to be. So, even though you're far from the limit, there's likely to be a tangible and subjective steering feel improvement with a 40/60 vs a 50/50 in the same way a RWD car's steering feels better than a FWD car's steering.

MrStuff

Although i've never driven the B7 that aggressively (only a rental! :P ) I found that ESP ON and ASR OFF (ASR is the real mood killer) the *** end of the B8 does not come out as much. With ESP on I find it more of a "point and punch it" ESP off makes 360s! :P

Anyways, personal exp!

mart242

ESP off requires driver skills.. ESP on = serving a frozen meal that you warmed in the oven and saying you cooked.