If there is a chink in the X6 M's high-tech armor, it's the brakes. The 15.6-inch, four-piston ventilated discs up front and 15.2-inch single-piston units at the rear started to fade toward the end of our lapping session. It takes a lot to slow a vehicle that goes this fast and weighs this much. Though the brakes never failed, the fade going into that last brake zone definitely increased the pucker factor a bit.

Inside the cabin of this four-seater is more of what we've come expect from BMW's M-badged vehicles. The M sport seats hold you comfortably and give you plenty of support when you hit the track. The standard M wheel is a nice addition to any vehicle, and the true left down, right up shift paddles are a great improvement over the up/down levers on other BMW automatics. Other interior highlights include an M driver's footrest, specific M instruments and functional displays, and, of course, the fourth generation of BMW's iDrive, along with all the other bells and whistles befitting a vehicle that lists for $89,725.

The X6 M defies all reason. BMW has made a big, tall, heavy truck drive and handle like a performance car, even if the brakes prove you can't really argue with the laws of physics. But one can't help wondering whether all that time, effort, and money would've been better spent on something more relevant to the storied M brand. Like a fast, light, highly fuel-efficient supercar.

2010 BMW X6 M
Base price $89,725
Vehicle layout Front-engine, AWD, 4-pass, 4-door SUV
Engine 4.4L/547-hp/501-lb-ft twin-turbo DOHC 32-valve V-8
Transmission 6-speed automatic
Curb weight 5300 lb (mfr)
Wheelbase 115.5 in
Length x width x height 192.0 x 78.1 x 66.3 in
0-60 mph 4.5 sec (mfr est)
EPA city/hwy fuel econ 12/22 mpg (est)
CO2 emissions 1.29 lb/mile (est)
On sale in U.S. Fall 2009