Track monster: Lapping at Circuit of the Americas in BMW's X6 M SUV

I used to think the BMW X6 M was a pretty stupid car. I didn't even much like the idea of the X5 M. A big, tall SUV with performance intentions? Then, for the X6 M, BMW lopped off the rear hatch, and along with it much of the practicality. I confess that I didn't much see the point.

And then I drove one, and everything changed. It was a few years ago, in Romania of all places. Romania is an interesting mix of new-world living in the urban areas and rather more antiquarian lifestyles out in the country. It has some of the best roads in the world (including the very best, according to Top Gear), but they're in consistently inconsistent shape -- smooth and fine one minute, rutted and torn the next. Even worse, other drivers seem to have little respect for their lives or anyone else's, while the livestock grazing on the side of the road add extra opportunities for carnage.

A traditional sports car would be ripped apart by the awful roads, and offer little protection from impatient drivers or cows in search of greener pastures.

In this (admittedly rare) combination of circumstances, I was lucky to have an X6 M at my disposal for a few days -- and here it was in its element. As fast and nimble as a 5,000 pound car can possibly be, accelerating hard and cornering respectably well, yet able to absorb the worst of potholes and float across rutted dirt roads, all while offering enough passive and active safety features to make me not worry about becoming a statistic.

For the launch of this car, the new 2015 X6 M, BMW brought me down somewhere a little closer to home: Austin, Texas. Here, the perfectly flat, impeccably smooth surface at the Circuit of the Americas is a far cry from the Soviet Bloc-era asphalt spread across Romania. However, America's newest and flashiest Formula One circuit offers enough dips, climbs, curves, straights and bumps (in the form of rumble strips) to put any kind of car to the test. It's a test that the new X6 M passed with flying colors.

BMW's 2015 X6 M makes big steps forward under the hood, with the 4.4-liter twin-turbo V-8 upgraded to 567 horsepower and 553 pound-feet of torque. That's a lot of go, able to haul this 5,185-pound beast from zero to 60 mph in four seconds flat. When it's time to stop again, massive six-piston calipers squeeze cross-drilled, 395mm vented disks.

Accelerating and braking such a sizable conveyance requires a lot of grip, offered by 21-inch Michelin Pilot Super Sport tires at every corner, 285/35 up front and a meaty 325/30 at the rear. (If that's a little too low-profile for your tastes, 20-inch wheels are an option.) Dynamic, electronically adjustable dampers and roll bars keep things moving in the right direction, as does a new set of differentials that not only shifts power from front to rear, but can vector torque left and right to help sling the thing around corners.

The works have been tied to a new electronic Dynamic Stability Control (DSC) system that, BMW says, offers a "bigger, better controlled slip angle" before cutting in and ruining the fun.

This, I would learn on the track, is not just marketing-speak. Slot into the interior and you are dazzled with an array of buttons controlling every aspect of the car. Most of the dynamic choices -- suspension, throttle, steering, transmission -- offer three levels of increasing absurdity. Before heading out onto the track I dialed them to all their Sport+ settings, giving the stiffest ride, most power, firmest steering and most brutal shifts. (However, I would quickly reset the steering back to Comfort, as the firmest setting just slows things down.)

Each tap of a button gradually transformed this SUV into something different, something BMW calls a "Sports Activity Vehicle." Even the heads-up display, projected onto the windshield, morphed from a simple speed indicator into a Formula One-style tachometer, blinking red when it was time to tap the right paddle and grab the next of the eight gears on offer. Hard shifts are greeted with a raucous snarl from the exhaust and a firm kick to your backside.

Slicing through the famous S-turns at the Circuit of the Americas, doing my damndest to chase down BMW pro driver Bill Auberlen, the X6 M not only changed direction quickly and capably but stayed remarkably flat while doing so, something you wouldn't expect from a thing as tall as this. It also got properly loose, even with the DSC enabled. Driven on edge the car constantly moves about, rear slowly braking away when I accelerated too early out of fast turns, front washing out when I carried too much speed into the tight ones.

In other words, the big X6 M felt remarkably balanced, and the DSC allowed enough slip for me to feel like I was correcting my own mistakes before it stepped in and properly saved my bacon. Knowing that I had that safety blanket let me push the car harder than I normally would have on an unfamiliar track, yet it didn't ruin any of the fun.

Neither did the turbos. The throttle response may be a hair less sharp than a free-breathing V-8 of yore, but you'd barely notice. Down the long back straight, the V-8 let me touch 150 mph before it was time to step on the brakes and rein the thing back in. The left pedal travel is long and the feel is soft, definitely at odds with the otherwise harsh nature of the car, but the overall braking performance never wavered. Cool weather admittedly helped the situation, but lap after lap, the X6 M stopped straight and true.

The 20-way power-adjustable sport seats kept me firmly in place -- or they did once I set the adjustable bolsters to squeeze me like a straight jacket. However, with the seat at its lowest position, my preferred placement for sporty driving antics, the steering wheel felt too high. It, too, is power-adjustable, but didn't tilt down far enough for my tastes.

Out on the streets surrounding Austin, the X6 M required another reconfiguration Here the Sport+ suspension is far too harsh, with even Comfort mode providing a very firm ride. The eight-speed transmission, on its raciest mode, barks and kicks with every shift and will stubbornly let you ride the rev limiter as long as you like. That, too, needs to be toned down with the press of a button for the road.

With everything backed off, and with the heads-up display telling me speed limits rather than shift points, the X6 M felt quite good. However, the car never truly hides its sporting pretensions. Even on full Comfort mode the ride is far from cosseting, though at least the transmission and power delivery soften considerably. And of course, the entire package is augmented with safety niceties like lane-departure alerts, adaptive cruise and blind-spot warnings.

The interior, meanwhile, is a very sophisticated place to be. The seats are firm but comfortable and offer both heating for the winter and cooling for the summer. Materials are quality throughout, with only the flip-down sunglasses holder mounted in the ceiling feeling slightly low-rent. The Alcantara headliner is seamlessly applied and feels fantastic.

BMW's two big power wagons, the X5 M and X6 M (pictures)

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Step outside of the car and you cannot ignore that this is a curiously proportioned beast. To me it looks closer to a Dakar rally entrant than something destined for the road; tall and chunky around the wheels yet taut and shapely above the hips. It's so big that even the 21-inch wheels look merely adequate, and you'd never realize the six-piston calipers within are nearly as large as an American football.

The massive vents in the front look gratuitous, but they are functional, ducting air through 10 separate cooling devices. Intercoolers, oil coolers, radiators -- needless to say, making something this big go this fast generates a lot of heat.

The most controversial part of the styling is, of course, that slanted rear roof, the most notable difference between this and the virtually identical X5 M. It's a willful disposal of cargo space, an almost ostentatious shunning of usability strictly for the sake of statement.

But what a statement. The X6 M is a curious machine; a car that is big and tall and heavy and fast not for practicality's sake but just because it can be. By all accounts, the X5 and X5 M are more practical choices, and the $103,050 starting price on the X6 M certainly won't help it win any converts, but if I ever find myself making a spirited trip across Romania again -- and I certainly hope that I do -- the X6 M, which hits dealerships in March, would still be my choice. (Because this event was focused on the US market, pricing and availability in other countries such as the UK and Australia weren't discussed. Once that information becomes available, we'll update this article.)

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