xDrive

[Mitch P.]

also, I'm guessing that the 10+ sec trick would disable the ABS from braking one particular wheel once it starts spinning. Thus, at most you'd have one front tire and one rear tire spinning at the same time. Kind of like two open differentials front and rear which is essentially the case. BMW is relying on the ABS system to brake one wheel which in turn transfers torque to the other side of the car.

Quattro has front and rear EDL's (electronic locking diffs) as well as a center torsen (TORqueSensing) differential providing automatic and variable front to rear distribution.

[DinanX5]

Originally Posted by B&DCalgary

You have a slight misperception about traction ... Slowing the rotation of the tire to prevent spinning actually maintains traction, and a non skidding tire will always provide better traction and better acceleration than a spinning tire ...
The only time spinning the tire might be an advantage is if the snow is so deep and soft that you can't get traction, then spinning the tires can sometimes burn down through the snow to the point where it hits pavement.

No mis-perception here - that's an example of a situation I had in mind... seen it happen several times. I've also (in my snow-tired 328Ci) had TC actually slow the vehicle to a stop when climbing an icy hill b/c the wheels could not find enough traction to keep them from spinning. After switching off DSC/DTC, from a dead stop, I was able to scoot right up and over the hill by keeping the wheels carefully and slowly spinning (like 2-3K RPM).
I'm aware of the physics of traction as well, but I've found that sometimes the real world deviates from academic theory.

[DinanX5]

Originally Posted by Mitch P.

I'm guessing that the 10+ sec trick would disable the ABS from braking one particular wheel once it starts spinning. Thus, at most you'd have one front tire and one rear tire spinning at the same time. Kind of like two open differentials front and rear which is essentially the case.

Makes sense... that would be very cool, actually. Tough to verify though - unless you enlist a buddy to stand outside the vehicle in the snow and watch what the wheels are doing.

[E61Silver]

I remember seeing a video of the X5 and a Audi going up a snow covered hill and the Audi won. Do any of you still have the link?

[DinanX5]

Originally Posted by x54.4blue

I remember seeing a video of the X5 and a Audi going up a snow covered hill and the Audi won. Do any of you still have the link?

Dude, look 4 posts up...

By the way, judging from the stock prices rolling across the bottom of the screen in that video, it's circa early-2001... which means that the X5 is not the facelifted xDrive version. I'd like to see a re-test of Quattro vs. xDrive!!

[E61Silver]

Originally Posted by DinanX5

Dude, look 4 posts up...

By the way, judging from the stock prices rolling across the bottom of the screen in that video, it's circa early-2001... which means that the X5 is not the facelifted xDrive version. I'd like to see a re-test of Quattro vs. xDrive!!

[DinanX5]

Originally Posted by x54.4blue

Mitch P's post... 4 posts before yours.

Here:

Originally Posted by Mitch P.

...http://video.google.com/videoplay?do...4614&q=allroad

Allroad in this video vs the others up a ski slope. Cool stuff!

[E61Silver]

So the BMW 3 and X5 didnot have X drive?

[B&DCalgary]

That Audi video looks a bit suspect to me. The Audi looks like it's about to die before it gets anywhere near the camera (tires are spinning and it has lost momentum), then it cuts to a shot of it going past the camera so fast it practically takes air of a bump.

I also wonder what they did about equalizing the tire/wheel combos between vehicles. If they aren't running the same model and width of tires, then the comparisons are meaningless if you're trying to compare the abilities of the AWD system.

[E61Silver]

It also looked like the Allroad was making a faster approach that gave it an advantage. It sure did not look very scientific.