German Car Forum

Sighted! The abominable snow van!

The 2009 BMW X6 in the snow.

If you look closely at the picture, you’ll see something hideous. Something horrible. Something… abominable. Yes, kids, it’s the abominable snow van.

Looks aren’t everything, of course. And you may actually like the way the BMW X6 looks. I don’t. But there’s one thing we can’t disagree on: the X6’s ability to mask its 5300-lb weight and dance like a ballerina when things get slick.

I had the pleasure (and I do mean that) of spending a long evening with this particular X6 in below-zero (Fahrenheit) temperatures and on snow-covered roads. An xDrive50i model, it was outfitted with the twin-turbo, 400-hp 4.4-liter V-8 and, uh, summer performance tires.

So grip—whether braking, accelerating, or cornering—was near zero. Slight grades that presented no challenge to front-wheel drive sedans on all-season tires were, at best, a “maybe” proposition in the X6. Not the car’s fault—it should have been wearing winter rubber—but the lack of grip gave me the opportunity to really test the X6’s over-the-limit handling behavior at safe speeds.

And… Oh My God.

I thought the hours I had spent flogging the X6 in the dry—and on wet skidpads—were enough to know that its trick rear differential was amazing. And I was right, but in near-zero grip conditions, the system’s performance becomes mind-blowing. Poor executive editor Joe DeMatio, who thought he’d be winding down for bed after a few glasses of red wine over dinner. Instead, he listened to a half-hour of hyperactive physics babble from me.

The X6’s Dynamic Performance Control differential, if you’ll remember, can actively shuffle power between the rear wheels. Unlike a limited slip diff, which progressively locks the two wheels together (transferring, at most, half of the torque to each wheel), the X6’s differential can send all of the power to one side. Powering only one side of the car creates a moment that wants to pivot the car in one direction or the other.

Rather than just use the diff’s advantages to help put down power, BMW’s engineers have programmed the whole system to assist in turning the X6 (to reduce understeer) or resist turning (to reduce oversteer). The system works both when there’s power being put to the ground or engine drag trying to slow the vehicle.

BMW’s stability control system has a reduced-intervention mode called DTC that lets the X6 get a little sideways, and the mode best takes advantage of the diff’s magical ability to turn the car. Conventional stability control systems pull power (almost entirely) and forcibly brake one or more wheels to keep the car under control accelerating around turns in slippery conditions. The result is a disjointed, head-bobbing, and ultimately, very slow process.

The X6, on the other hand, just smoothly goes around the turn. Using the differential to help turn the car (as well as the active steering system), only occasional computer-initiated stabs of the brakes are necessary, and the engine’s power doesn’t need to be cut nearly as much.


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