Ed Hellwig, Executive Editor
Professor Ulrich Bruhnke is the head of BMW's Motorsport division. He's a big, burly German who would be quite intimidating if he didn't smile so much. Before BMW, he headed up the AMG arm of Mercedes-Benz. This guy knows horsepower.
After a few laps around Spain's Jerez road course in the new 2006 BMW M Roadster, a high-performance version of the standard Z4, Bruhnke is smiling again. He hardly seems the roadster type, but the big German is grinning like a Jimmy Carter impersonator as he puts the spurs to the little convertible. Apparently 330 horsepower can make even the otherwise tame Z4 satisfying to Germany's sultan of speed.
Transforming the ultimate shower gift into the manly M Roadster wasn't as difficult as it sounds. Take the most masculine BMW there is, the soon-to-be-replaced M3 coupe and swipe all of its best hardware. We're talking everything from the engine, steering system, brakes, variable differential lock and a handful of suspension parts. M Roadsters also have unique 18-inch wheels and bodywork, not to mention 218 fewer pounds to carry around compared to the M3.
Our turn at the wheel Sitting lower to the ground than the already low Z4, the M Roadster isn't the easiest car to get into. You swing the door past your knees and then try to look graceful falling into the seats, which in this case come standard with leather and extra bolstering. Although you sit deep in the cockpit, the view over the arched dash is still good. There's enough legroom for 6-footers but the cockpit feels tight.
Big analog gauges with red needles sit behind a thick Motorsport steering wheel. The tachometer is also Motorsport spec, with a variable redline that settles at 8,000 rpm when the oil is fully warmed up. The speedometer reads to 180 mph, but the computer will cut you off at 155 mph.
Our test car's interior is drab in all black. It's a mix of good-looking plastics and a new trim option BMW calls "Carbon Leather." It's black leather with a carbon-fiber pattern, and although the combination doesn't look as ridiculous as it sounds, the metallic trim which comes standard looks better. Everything else is similar to the Z4 in design and feel except for the automatic climate-control knobs. They get extra rubber trim around the edges for better grip during those tricky midcorner fan-speed adjustments.
All the right hardware There's no annoying start button as in the 3 Series, so you turn an actual key to fire up the M Roadster. The 3.2-liter straight six is identical to the M3's so it has an iron-block, double VANOS variable valve timing system and an 11.5:1 compression ratio. A slightly more restrictive and quieter exhaust shaves off 3 horsepower, leaving the M Roadster with an official rating of 330 hp at 7,900 rpm. Torque remains the same at 262 pound-feet at 4,900 rpm.
A new six-speed manual transmission is used since the M3's six-speed didn't fit. It's the only transmission available and its final gear ratios are virtually the same as in the M3, yet BMW claims a quicker 0-60 time (4.8 to 4.9) for the heavier coupe. It couldn't explain why.
You'll never miss the extra tenth Like most BMWs, the M Roadster feels stronger than its horsepower and torque numbers suggest. Other than a little softness below 2,500 rpm, it's strong enough to smack your head off the roll hoops with a jab of the throttle. Pressing the "sport" button has a less noticeable effect than it does in the M3. Instead of an instant quickening of the throttle's reactions, the M Roadster has a more subtle program that only kicks in after you get into the gas a little further.
The jury is still out on the exhaust note. The M Roadster was tuned for a softer tone than the M3 but it's still a mix of raspy straight six and what sounds like a loose catalytic converter. There's no question about the new gearbox — it's perfect. Unlike some BMW shifters which can feel a little delicate, this stick can be slammed through the gears as fast as you can rip it.
Although the M Roadster shares its steering system, brakes and numerous suspension parts with the M3, most of the parts were tuned specifically for it. The ride quality is noticeably better than the M3 on the street. It's remarkably stiff for a convertible, yet you rarely get any harsh impacts. Steering feel is about perfect and the brakes are way more than you'll ever need for the street.
Track time In addition to our time on the street we did a few laps of Jerez ourselves. As stiff and precise as the M Roadster is at normal speeds, rip through a corner fast enough and there is body roll. Not your typical sloppy, convertible kind of roll, but enough to let you know when you're approaching the limits.
Compared to the Z4 roadster, the M Roadster has a half-inch-wider track, reconfigured lower control arms and a new rear subframe that allows it to run the same Variable Differential Lock used in the M3 and M5.
Get to the limit and the Dynamic Stability Control system shuts things down with reduced throttle and a few grabs of the brakes. It won't stop you dead in your tracks like some systems, but having any real fun still requires shutting it off completely, a feature BMW still thankfully offers.
With the electronic governors turned off, you begin to appreciate how well the variable limited-slip differential distributes the power. Combined with plenty of traction from the 255/40 tires in back, the M Roadster launches out of corners as fast as its brakes will let you dive into them. The massive cross-drilled rotors are the same ones used with the M3's competition package and although they shrieked for mercy after each lap they never failed to provide plenty of stopping power.
Get your priorities in order With a base price of $51,300, the 2006 BMW M Roadster will run you $2,400 more than an M3 coupe. That doesn't make the roadster much of a bargain considering it isn't any faster and has two fewer seats and a smaller trunk.
Compare it to other high-performance convertibles, however, and the M Roadster is the new king of performance per dollar. It's not only $3,400 cheaper than a Porsche Boxster S, it's $10K less than a Mercedes SLK55 AMG. And if BMW's numbers are correct, the M Roadster is faster than both.
Somewhere out there Mr. Bruhnke is smiling.
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