BMW hopes to win over snobbish roadster purists with the launch of its all-new update of the Z4.

Climbing into the southern extremes of the Swiss Alps, I muscle the ancient roadster into a corner, well aware of the way its skinny tires have begun to slide on the wet pavement.  The guardrails are few, even though the drop-offs are becoming increasingly steep.  As I steadily climb higher, the rain morphs into snow, the wind whipping it in through the open cockpit.

Spend a few hours behind the wheel of an antique BMW 315 and you understand the classic definition of roadster.  Fun, absolutely, but it’s also primitive, cramped even dangerous when road conditions are less than perfect.  So it’s not hard to understand why I jumped at the opportunity to swap out for the car my traveling companion had chosen for the day, a 2009 BMW Z4.

The name may be familiar, but the ’09 roadster is a very different beast from the one you might already know.  It is, for one thing, the first complete makeover of the Z4 since 2002.  Among other things, the Bavarian maker has opted, this time, for a foldaway hardtop, rather than the canvas roof that the old Z4 shared with BMW roadsters dating back to my pre-War 315.

With its new 3.5-liter twin-turbo Inline-6 and double-clutch transmission, the Z4 can launch from 0 to 60 in about 4.8 seconds.

That decision underscores the more significant transformation of the new model from a limited-use sportster to a sporting, every day driver.  But, in the process, has BMW expanded the definition of roadster or stripped it of its soul?

There are, of course, plenty of advantages to going with a folding metal roof.  In the case of the 2009 BMW Z4, it can open or close in less than 20 seconds.  With the top up, you increase both safety and security, factors that appeal to buyers in many parts of the world.  With the roof up, the new Z4 is also about as comfortable and quiet as any BMW hardtop.  And to some folks, that’s part of the problem.

You also insulate yourself from the world, precisely the opposite of what a roadster is supposed to be all about.  Indeed, the folks at BMW’s sibling division, Mini, may have captured things perfectly with their campaign to promote their latest convertible, going so far as to build in a new “Open-meter” that shows just how much time you’ve driven with the top down.

So, for purists, the ’09 Z4 may not resonate, but for most of the rest of the world, its design, poise and balance should absolve it of most, if not all, sins.

BMW is the latest automaker to make the switch to a foldaway hardtop, for its 2009 Z4. The decision has safety and security advantages, but comes with a sizable weight penalty.

I must admit I was never a fan of the Z3, which brought BMW back into the roadster market.  The ’02 Z4 was a definite improvement, but the design was still a bit awkward and ungainly.  With the ’09 redesign, BMW finally has it right, visually, the new roadster is the most attractive in a segment that includes such competitors as the Porsche Boxster and Mercedes SLK.  From nose-to-tail, you know it’s a BMW, with the low-slung kidney grille, the sculpted lines of the fenders and doors, the sensually curvaceous roof and the short tail that conceals an unexpectedly useful trunk – one capable of holding two full-size golf bags, should you choose the optional winter package, which includes a ski pass-through.

To pull it all together, the new Z4 had to grow a fair bit.  It’s a half-inch wider and six inches longer than the model it replaces, and when you factor in the machinery of the hardtop, a full 500 pounds heavier, at 3494 pounds for the base roadster.  If BMW designers and engineers hadn’t worked so closely together, that would’ve been a fatal error, but more on that in a moment.

The 2009 BMW Z4 roadster boasts a much improved interior -- and the first use of iDrive in the automaker's roadster family.

The roadster’s interior has also undergone some significant changes.  The overall look is decidedly more upscale and elegant than BMW’s past roadsters.  It reflects the same sort of thinking as the new 7-Series, with graphics that are both delightful and quite functional.  Controls are easier to operate and better positioned.  The big news, though, is the addition of an iDrive controller for the first time.

To our good fortune, that’s the new iDrive, which first debuted on the all-new 7-Series, just last autumn.  After years of criticism, BMW finally accepted reality and added an assortment of buttons, which make it far easier to access such things as the audio and navigation systems.  As with the decision to go hardtop, BMW won’t satisfy everyone, especially those who prefer a unique button for every system and function.  But while the new iDrive still has a few flaws, it is far more intuitive and easy to operate than the system that came before.

With its pop-open navi screen, an audiophile sound system and a climate control system designed to keep you comfortable, even with the top down on a bad day, it might be easy to dis the new Z4 as a roadster poseur.

Making it even easier to downplay its credentials is the fact that the 2009 BMW Z4 is so darned comfortable to drive.  No, it’s not a Buick, soaking up every bump and pothole, but it comes reasonably close.  As said, earlier, this is a car that could become a daily driver in all but the snowiest road condition.

Indeed, even there, the roadster proved itself both agile and competent.  On the highest, sharpest mountain passes, the new Z4 maintained its grip, even when marbles of ice and snow began forming on the pavement.

Unlike the roadsters I’d grown up with, you don’t have to muscle the Z4 around.  It’s as nimble and responsive as anything else now on the market sporting the automaker’s “spinner” badge.  Despite the smooth ride, there’s a definite sportiness to the ’09 Z4’s manners.  The suspension holds true, allowing only the most minimal body roll, even charging some of the worst switchbacks we experienced on the drive from Lake Como to Zurich.

The Z4 now comes with Dynamic Drive Control, and can now be configured with an adjustable M suspension.  You’ll have the choice of conventional, sport and sport plus mode.  Both sport modes enhance throttle responsiveness, while steering becomes tighter and heavier.  Sport plus limits the traction and stability control systems, so you can hang the rear wheels out a bit.

Meanwhile, the optional M suspension sits nearly a half-inch lower, while its adjustable dampers firm up in sport modes.

What proved particularly impressive was the new driveline in the version we drove.  Badged sDrive 35i, it features a twin-turbocharged inline-six making a solid 300-horsepower – about as much as the old M version.  That alone would deliver a great ride.  Now, mate that to BMW’s new twin-clutch gearbox, a slightly-revised version of the transmission offered in the latest M3.

Those who recall the electronically-shifted manual found in the M5 shouldn’t abandon all hope.  Quite the contrary.  While the new DCT delivers lightning-fast shifts, it doesn’t jar your fillings out in the process.  Leave it in automatic, if you wish, or put it in manual mode and operate the steering wheel-mounted paddles.

(The shift pattern is one of the differences between the Z4’s twin-clutch gearbox and the M3s.  Second gear is slightly revised, as well, and there’s no adjustable shift program.)

For those looking for a little less power, BMW will also offer a 3.0-liter 6-banger making 255 horsepower, by the way.  That’s still a 40 hp bump from the comparable ’08 offering and should deliver improved performance, despite the added weight.

As to fuel economy, BMW will release that shortly, but  look for a moderate improvement, the automaker says.  With the 3.0-liter ’08, the Z4 delivered 18 mpg City, 28 Highway.  The 3.5 should come in closer to 18/27, but it will also launch you from 0 to 60 in about 4.8 seconds and reach a governed top speed of 150 mph.

The Z3 wasn’t a favorite of roadster purists, who tended to view it as a “secretary’s car.”  And the original Z4 had plenty of detractors, as well.  It remains to be seen if the new car will finally get the attention it deserves from those who think a classic BMW 315 is the ultimate roadster archetype.  Ironically, the ’09 could be written off because it does so much so well.  But that would be a shame because, well, it does so much so well.  It’s a great every day car, but pull down the top, breathe in some open air, and consider that maybe, just maybe, it’s the dictionary definition of what this generation’s roadsters should look – and drive – like.