NEWBURY PARK, CA – Just in time for a summer of weekend getaways, golf outings and top-down meandering, BMW AG delivers the all-new ’09 Z4 sDrive roadster.

With a retractable hardtop as its most dramatic upgrade, the zippy convertible will calm a mid-life crisis while fulfilling a vain desire to one-up drivers stuck in minivans and practical sedans.

Whether the Z4’s iterative styling is enough to retain leadership among luxury roadsters is the big question.

Mechanically superb, the Z4 meets every challenge thrown its way, delivering a thrilling ride with more power and BMW’s sharp chassis dynamics, thanks to a near 50/50 weight distribution.

This despite tipping the scales some 300 lbs. (136 kg) above the previous-generation Z4 due to the extensive hardware associated with the retractable hardtop, as well as a longer rear overhang to accommodate the top when stowed, while still allowing limited cargo space.

Still, the new Z4 seriously outguns its predecessor, which offered one engine: the 255-hp 3.0L inline-6 with magnesium-aluminum block that won Ward’s 10 Best Engines honors in 2006 and 2007.

That marvelously smooth powerplant remains the base engine in the new roadster, but the 300-hp direct-injection 3.0L twin-turbo (a 3-time 10 Best Engines winner) is a delectable addition.

Channeling all this power are the familiar and excellent 6-speed manual and 6-speed automatic transmissions that continue to shift with glorious precision.

Another addition is BMW’s newly developed 7-speed double-clutch sport automatic, first introduced in the M3. Paddle shifters can be used with both automatics.

According to the spec sheet, the DCT-equipped roadster can find 60 mph (96 km/h) in 5.0 seconds, while the sDrive35i without it settles for 5.1 seconds.

BMW executives say 50% of M3 buyers are opting for the new DCT, and the take rate is expected to reach 75%.

The Z4 take rates for the transmissions are forecast at 80% for the two automatics and 20% for the manual. BMW engineers say the 7-speed DCT should get better mileage than the 6-speed manual in the sDrive35i, although the press kit officially pegs both at a 20 mpg (11.7 L/100 km).

Meanwhile, the combined fuel economy for the sDrive30i with the less powerful I-6 is rated at 22 mpg (10.6 L/100 km) for both the manual and 6-speed automatic.

Those numbers are fairly accurate, based on our test drive of both engines. Under a heavy boot, the 300-hp Z4 manages to stay above 20 mpg, according to the trip computer. With a moderate throttle, 27.3 mpg (8.6 L/100 km) in the same car isn’t difficult.

Like the previous roadster, the new Z4 features electrically assisted power steering, which is remarkable considering BMW’s fastidious embrace of hydraulic power steering over the years.

Turn-in remains just as linear with EPS, which boosts fuel economy and manages to provide just the right amount of assist in every driving situation.

The only complaint about the steering system left the BMW engineers stumped. During our drive, each time the cruise control was shut off, the steering momentarily felt numb and stiff, as if on auto-pilot, before quickly correcting itself.

’09 BMW Z4 sDrive35i
Vehicle type Front-engine, rear-wheel-drive, 2-passenger roadster
Engine 3.0L twin-turbo DOHC all-aluminum I-6
Power (SAE net) 300 hp @ 5,800 rpm
Torque 300 lb.-ft (407 Nm) @ 1,400 rpm
Transmission 7-speed dual-clutch
Wheelbase 98.3 ins. (250 cm)
Overall length 166.9 ins. (424 cm)
Overall width 70.5 ins. (179 cm)
Overall height 50.8 ins. (129 cm)
Curb weight 3,494 lbs./1,585 kg
Base price $52,475
Fuel economy 17/24 mpg (13.8/9.8 L/100 km)
Competition Audi TT, Mercedes SLK, Porsche Boxster, Honda S2000
Pros Cons
Mechanically superb Warmed-over styling
Gorgeous interior Ergonomically challenged
Show off with folding top Golf clubs don’t fit

Standard on the Z4 is Dynamic Drive Control, which allows the driver to choose between three drivetrain and suspension settings at the touch of a button.

High-performance brakes provide sure stopping power while reducing weight, and the Z4 is the first car in its segment to feature an electric parking brake controlled by a button on the center console. The Z4 rides on 17-in. aluminum wheels shod with run-flats. Like the previous roadster, it has no spare tire.

In the front, a lightweight “double-jointed” mostly aluminum suspension features traditional struts, and a constant-geometry axle supports the rear.

Optional as part of the Sport package is BMW’s Adaptive M Suspension with electronic damping control. A central microprocessor varies the compression and rebound stages on the four twin-sleeve gas pressure dampers for optimum response.

BMW says the system is so fast that a rear damper braces in time for the impact of a pothole the front wheel already has struck.

This type of gee-whiz technology is exactly what the world has come to expect from Bavaria’s brightest engineers. The world also expects innovative styling from BMW, but it’s lacking in the new Z4.

BMW’s mystique depends on dazzling well-heeled customers with powertrains, gadgets or styling they didn’t know they wanted but soon couldn’t live without.

Sure, the new Z4 offers a masculine and shapely clamshell hood, but the overall styling leaves the casual observer oblivious that this is a new BMW. From the front and side, the new Z4’s sheet metal is far from groundbreaking.

When the first-generation Z3 roadster arrived in 1996, assembled at an all-new plant in Spartanburg, SC, it made a strong first impression and provided a competent thrill ride for James Bond.

The next generation came along as the Z4, with a completely different look and markedly enhanced performance. BMW marketed the new roadster as “the land shark” because of the beltline that ascended toward the front of the car, as well as its foreboding presence.

With the exception of the significantly redesigned back end, the new Z4 looks too much like its predecessor.

But BMW has proven the automotive press wrong before, especially with the controversially styled but successful previous-generation 7-Series flagship.

And the sales figures in Ward’s Luxury Sport segment may hold the answer as to why BMW kept intact the previous-generation Z4’s design vocabulary.

Since 1996, BMW roadsters have clobbered the competition. Only in 2005 did the Mercedes SLK outsell the Z4, by 1,200 units. Along the way, the Z3/Z4 racked up four years of 20,000 deliveries.

But since 2006, Z4 sales have fallen and redesigned rivals such as the SLK and Audi TT are closing in. BMW declines to predict how many new Z4s it will sell as production ramps up in Regensburg, Germany.

With its performance pedigree, the new convertible will do fine, and buyers who loved the previous roadster will love this one, too.

Watching the retractable hardtop – a first for the Z4 – perform its mechanical ballet in a mere 20 seconds with the fluid precision of the Bolshoi is darn near worth the sticker price by itself.

But in convertible mode, the trunk is maddeningly short of space. A set of golf clubs will not fit when the top is down. For those interested in a fixed hardtop coupe version, the auto maker says there are no plans.

Inside, the Z4 is well-appointed with beautifully stitched leather trim in shades of bold crimson and creamy ivory to add flair. The roadster effectively applies brushed aluminum trim familiar in other BMW interiors.

Ergonomically, the Z4 is challenged, as are many roadsters.

One cupholder clips in place to the right of the center stack, always knocking the passenger in the knee. Another cupholder resides in the center console but only can be used when the armrest is raised. Big Gulps need not apply. Storage space behind the seats is minimal.

The iDrive controller mounted in the center console has become increasingly intuitive and user-friendly.

Another complaint centers on the door sills, which bear the BMW badge in faux plastic chrome – and it’s not illuminated. Meanwhile, owners paying half as much for the Nissan 370Z open the door to find a beautifully crafted “Z,” shining as if by firelight.

Pricing starts at $46,575 for the sDrive30i and $52,475 for the sDrive35i. Options such as the 7-speed DCT ($1,525), navigation ($2,100), M suspension ($1,900) and exclusive ivory leather ($2,050) drive the sticker price well past $60,000.

Roadsters exist to remind us of the joy of driving. For many buyers who never forgot this, the Z4 will fit handsomely in their personal fleets.

Those requiring breakthrough styling from cars of this nature might do more cross-shopping.

tmurphy@wardsauto.com