Poles apart - BMW X6M X5M

More than any other cars in this issue - and maybe more than any other cars this year - you're going to have strong opinions on these two. Some of you will be delighted that BMW has had the brass balls to give the full M-treatment to its X5 and X6 off-roaders and launch these 395kW monsters into an economic and environmental hurricane. I'd partially agree. Drifting them over a frozen Swedish lake, V8s blaring and sucking their way through litre after litre of premium unleaded seemed gloriously, wilfully contrary to the current popular mood. I felt like a latter-day Nero, fiddling with the traction control while modern Rome burns. Some of you, however, will be outraged that BMW is building these cars, or at least puzzled as to how it hopes to make any money from them right now, or repair the damage they'll do to the green image it's trying to nurture. But the majority of you, we suspect, will focus less on how the X5M and X6M relate to current global economic and environmental crises, and worry instead about the most pressing issue facing us today: what these two SUVs mean for the reputation and future of BMW's fabled M badge.

We're the first people outside BMW to drive them, and we've come to Arjeplog, its winter test centre in northern Sweden, to do so. Yet as our twin-prop plane shimmies down onto a perilously white runway, BMW still hasn't officially owned up to them. Both will be revealed in April; the X5M at the Shanghai show, and the X6M a few days later in New York.

We have a prototype of each to drive. Both still wear camouflage, but underneath they're pretty much finished.

Arjeplog is as weird as its name suggests. It lies at the centre of a vast wilderness with 8000 lakes and just 2000 people. Each winter around 1000 car engineers pass through, working on the 40-odd test tracks that are carved out on the lakes from December, once the ice is 30cm thick. It's indescribably beautiful up here - and indescribably cold. At minus 33°C, the moisture in your nostrils freezes as soon as you step out of the car. But that's why the engineers come.

The work is mostly dull; fine-tuning of braking, traction and stability control systems on the ice, and proving that a car's systems work in real cold climates and not just the giant fridges back at base. At least the M engineers get to drive something interesting to relieve the boredom.

The two big controversies around the X5 and X6M - timing and credibility - are closely linked. The implosion of the car market has already made BMW bin the 7 Series-based Concept CS four-door coupe and the stretched X7 SUV. Both of those vehicles would have needed extensive and expensive re-engineering of the platforms on which they're based and wouldn't have sold enough to cover their costs. Like those two cars, work began on the M SUVs in happier times, but BMW can afford to continue because they're not costing as much to create. The real issue for M obsessives here isn't just that the division is breaking all its cardinal rules at once by abandoning naturally aspirated engines, rear-wheel drive and manual gearboxes, and putting its badge on an SUV. It's also that the X5 and X6M just aren't that different to the standard cars underneath. They have the same engine, same 'box, same driveline as the standard turbocharged V8s; all tweaked by the tuning division, but lacking the 'otherness' that has come to define an M car.

M's people are unapologetic about the new cars, and they make two good points about the engine. The first is that few anticipated how quickly turbocharged engines would improve; they're smaller, greener and quicker, and there's little cost to response or linearity. Expect more turbocharged engines from M in future, they hint, perhaps using this V8 in the next M5 and allowing the next M3 to go back to a straight-six. Secondly, they point out that what works in a road car might not be right in an SUV. Re-engineering the M5's V10 for four-wheel drive would be expensive and pointless when its 'thin' 520Nm at 6100rpm is already outgunned by the standard X6 V8's 600Nm between 1750 and 4500rpm. The V10 just wouldn't have got an M-badged SUV (carrying 400kg more than the M5) up and hustling fast enough.

They also reveal that M has, contrary to the message circulating, been considering an SUV for a while. It built the one-off, 514kW X5 Le Mans in 2000, and secretly fitted both a tuned 335kW E39 M5 rear-drive powertrain and the V10 from the current E60 M5 into X5 bodyshells. But why put one into production now? Because BMW needs to make money. The launch of the new M3 boosted M's sales by a staggering 50 percent last year. At best, the SUVs will sell ten percent of the M3's 18,000 units, but they'll be popular in markets like the Middle East and China where car sales are holding up better, and BMW is hoping they'll replicate just a fraction of the M3's mojo.

And don't be confused by the nomenclature; the fact that the M comes after the number is simply because the X was there first and in no way makes them second-tier offerings. "This is a real M car, with real M feel", a staffer told us, so they won't be shy with the styling. There are a couple of oversized air intakes at the front and a pregnant bonnet bulge. The hallmark M side vents have been covered over on our test cars, but are present. There are big rims and quad pipes at the rear, and in one car the beginnings of the full M interior treatment, with carbonfibre inlays, an expensive-feeling leather toproll, active seats and an M button on the wheel, even if it is just a sticker for now.

But what's under the hump? A version of the 4.4-litre V8 from the X6 50i, revised to make at least 395kW at first, rising to 410kW later, and around 700Nm. Same gearbox too; the six-speed ZF auto, with the mapping revised to give faster, later shifts. Same xDrive four-wheel-drive system, but with more torque dialled to the rear to give the illusion of what BMW calls 'standard drive', and less desire to shift it forward to counteract oversteer. The X5M will also get the clever Dynamic Performance Control rear diff, which accelerates the wheel with grip rather than braking the one that spins and until now was only offered in the X6. Brakes, suspension and steering will all be reworked, but they won't tell us how, wanting to keep a few secrets for the shows.

Nailed from rest on one of the few clear tarmac surfaces up here, the X6M is shockingly fast for such a deliberately solid, heavy-feeling car. A fat, instant gob of torque hits all four wheels and makes the nose rear up before booting the car off the mark, the needle surging evenly to the 7000rpm redline, where a quick, smooth change briefly knocks it back. The pace is definitely there; the standard 300kW X6 hits 100km/h in 5.4sec, and these cars' main rivals, the Merc ML63 AMG and Porsche Cayenne Turbo manage it in five dead. The X6 feels quicker still - maybe by a fifth of a second - but more tellingly a BMW engineer let slip that the X6M is fractionally quicker around the Nürburgring than a current M3. We're not sure if we believe him, but we're going to enjoy finding out.

But the way the pace is generated is unfamiliar in a BMW. The aristocratic, slightly manic engines in M cars usually require you to work them and their gearbox hard, for which you're rewarded with an edgy metallic rasp which speaks of high crank speeds and fine tolerances. This X6M is more like an AMG used to be, before AMG ironically went naturally aspirated. You just floor the gas, get a deep, loud burble overlaid with a little crackle on the overrun and instant, any-gear, any-revs thrust; more FPV F6 than V10 M5.

Limit handling is difficult to assess on sheet ice but there's clearly a lot right with the chassis and driveline of each car. With winter tyres and all aids engaged they turn and accelerate almost as if they're on tarmac. Like other M cars, the M button on the wheel allows you to choose your power output (300 or 395kW), damper setting and stability control level; all on, a Dynamic mode, allowing greater freedom to get the tail out, and all-off. In the latter, and in these conditions, you can feel the torque going to the rear axle and staying there as the cars pull long, composed drifts of which they show little sign of wishing to pull themselves out.

Any vagueness in the throttle, brakes or steering is magnified on ice, but the X5 and X6M are capable of absorbing and executing the most delicate instruction. Haters of sporty SUVs used to be able to fall back on the argument that a big wagon would always drive infinitely better, or they could until the X6 arrived. The standard version steers and handles with near-unbelievable precision and security. Sending more power to the rear axle seems to make it better yet, and makes overpowered SUVs a little harder to find absurd.

So what do we make of these cars? They're going to be titanically fast. They're probably going to redefine, again, how well you thought an SUV could drive. They are not going to feel as bespoke as M cars have until now. Dynamically - simple speed excepted - they will have little in common with an M3 or M5, but hint heavily at how future versions of those cars might be powered. They will also be among the least relevant cars to be launched this year, and we suspect they'll be an infrequent sight outside of Miami or Dubai. We still wonder why you'd pick an X6M over the already damned-quick X6 V8, or any X6 over an X5, or any X5 over a 5 Series wagon. But we can't help but like these two for standing facing into the overwhelming grey-green tide of public opinion, middle fingers extended, misguided, brave ... and probably doomed.

BMW X6M
Body steel, 4 doors, 4 seats
Drivetrain front engine (north-south), AWD
Engine 4395cc V8, dohc, 32v, twin turbo
Power 395kW @ 5500-6400rpm
Torque 700Nm @ 1750-4500rpm
Transmission 6-speed auto
Weight 2240kg (estimated)
0-100km/h 4.8sec (estimated)
Price $200,000 (estimated)
On sale Late 2009

BMW X5M
Body steel, 4 doors, 5 seats
Drivetrain front engine (north-south), AWD
Engine 4395cc V8, dohc, 32v, twin turbo
Power 395kW @ 5500-6400rpm
Torque 700Nm @ 1750-4500rpm
Transmission 6-speed auto
Weight 2270kg (estimated)
0-100km/h 5.0sec (estimated)
Price $180,000 (estimated)
On sale Early 2010