2009 BMW Z4

The proportion of hard tops to soft tops for convertibles and sports cars continues to evolve -- but not in the way you might think.









Increasingly, manufacturers are equipping their droptops with folding metal contraptions, despite their complexity and cost. The latest example: the 2009 BMW Z4, the first roadster from the Bavarian manufacturer with a hideaway hard top. It succeeds the Z4 Roadster and Coupe.

Others that have recently installed hard tops include Volkswagen's Eos, Infiniti's G37, Chrysler's Sebring and Mazda, which added a disappearing hard top model for its MX-5 Miata.

Usually, in addition to adding cost and lots of whirring and moving parts, a collapsible hard top reduces luggage space and accessibility, though there are exceptions like the MX-5.

But the counterintuitive thing about these engineering marvels is that they have appeared more on cars below the median price line than on the very expensive cars where you might expect them. For example, the $234,000 Bentley GTC Speed has a fabric top, as does BMW's own 650i convertible, which can wind up costing more than $100,000.

One explanation is that fabric technology has advanced to the point where convertibles really don't need hard tops because the soft tops likely can last the life of the car. And the super-luxury cars get tops that resemble the proverbial padded cell.

But Martin Birkman, BMW's manager of product planning and motor sports, has a better analysis of the hard top/soft top dichotomy.

A major reason BMW went to the hard top, he said, is to make the car more appealing to a larger array of people. Aside from the obvious advantage of a cozy car that feels like a coupe with the top up, Birkman says the hard top gives the Z4 more of the character of an everyday car.

He said a single person or a couple might consider using it as their only car, where people who buy expensive soft top convertibles likely view them as toys and not daily drivers. An example is the Audi TTS, a ragtop competitor of the new Z4 Roadster.

The new Z4 certainly is in a price class where it could be considered as an expensive toy. But the powers at BMW obviously also think the hard top will broaden its appeal, not to mention the fact that it replaces two models.

Still, it is not a car for the masses. The base Z4'sDrive30i has a starting price of $46,575 and you can option the more powerful sDrive35i up well north of $60,000. The tested 30i with the optional sport package and heated front seats had a suggested sticker of $49,375.

Though the more powerful 35i likely will find favor with poverty-challenged enthusiasts who just have to have the hottest version in the lineup, the 30i gets the driving juices flowing just as well.

It comes with BMW's famed 3-liter inline six-cylinder engine with 255 horsepower, which drives the rear wheels through a six-speed manual gearbox with a stiff shift linkage but glossy clutch action. The combination is good for a zero-to-60 acceleration time of 5.6 seconds and a top speed of 150 miles an hour, according to BMW's test figures.

If you opt for the $51,505 35i with the twin-turbo, 300-horsepower engine and the amazing $1,525 twin-clutch, seven-speed automated manual gearbox, you gain only six-tenths of a second, hitting 60 miles an hour in five seconds. Top speed is the same.

The seven-speed is a marvel, uncannily pre-selecting gears and snapping off shifts faster than you can think about them. But many enthusiasts likely would be just as happy with the tested six-speed stick shift and naturally-aspirated engine, not to mention saving nearly $6,500.

BMW calls the Z4 a roadster. By its definition, a roadster has a classic configuration of a long hood and a short rear deck. Years ago, a two-seater was considered a roadster if it had leaky side curtains. It was deemed a convertible if it had roll-up windows.

There's no point in arguing automotive theology. The Z4's defining characteristic is its way back seating position, almost over the rear axle. It imparts the feeling of driving the car from the back seat.

It's not a new phenomenon. The long hood/short rear deck has been a characteristic of many American muscle cars. Looking out over that elongated hood, as opposed to sitting in a sports car like a Porsche Cayman or Boxster where you can't see anything but asphalt, has a charm all its own.

The Z4 is a BMW, which means that by definition it is biased toward handling and performance, and that's what you get. It tracks cleanly through the curves and switchbacks and sends back tactile sensations and messages through the steering and brakes.