2005 BMW M5 vs. 2005 Mercedes-Benz e55 AMG - Full Metal Rocket

Beforehand, it seemed straightforward to predict the defining M5 moment. The tantalizing pre-launch specs had given enough clues: It was inevitably going to be the fraction of a second when the mighty 5.0-liter V-10 homed in on its 8250-rpm redline, when the head-up display flashed red, and when you tapped the transmission upshift paddle. In an instant, you'd be up into the next of the seven sequential ratios, the 10 individual throttle butterflies would've flipped wide open again, and the hungry M engine would hurl you onward in a brutal, hedonistic surge.

Which is exactly what happened.

It shouldn't have been a surprise. After all, that was what the last M5 led us all to expect. Sure, the old V-8 M5 handled okay, rode with aplomb, braked sternly, and was built like a tank, but it was, at heart, an engine car. The voice and power of its V-8 were what defined it. And if a 400-horsepower V-8 defined the old M5, then the new one, blessed with two more cylinders and another 100 well-bred ponies, was always going to be an engine car, too, yes?

Well, no, actually. The new M5's engine is, we're happy to report, the spectacular piece its specs would suggest. The sequential M gearbox aids and abets it by shifting cogs as promptly as any of its type. But the new M5 isn't just a powertrain car. It's a chassis car. The first full-effort curve--the moment when you load up the steering and feel the whole machine carve through the bend like a surgeon's knife, perfectly in tune with your will--that's the defining M5 moment.

"Lateral agility," they call it at BMW. While Mercedes-AMG has become fertile at siring ultrapower sedans, wagons, big coupes, and even SUVs, BMW M has held back. There is no M7, no MX5, no supercharger or turbo, either. An M car has to be responsive and fundamentally keen on turning as well as accelerating. The M5's technical spec is all about connecting the driver to a steed that reacts blindingly fast, whatever request the driver hands down.