Classic roadster proportions give the Z4 a long hood and short decklid, shoulders over the wheel arches and tapers in three axes. The creases begun at the inner edge of the headlight housings, roll over the front fenders and lead back to bisect the door handles, while opposite lower sweeps started at the front bumper curve upward to the rear wheels.
In side view it looks like a French curve over each wheel, the forward one twice the length of the rear, and from the driver's perch the hood seems to rise from the windshield base before falling off forward. We think it looks better with the top down but it's still relatively sleek top-up and has a similar closed profile to the big Mercedes SLR. Gills behind the front wheels carry the substantial badges and the side signal repeaters are now behind opaque panels in the gills; the BMW propeller logo is still here, but no longer serves to disguise the signal.
A variety of wheel sizes and finishes are offered, and while the Z4 is light and well-suspended enough that even 19-inch wheels can deliver decent ride quality, they might not work well with poor infrastructure (rough roads), and some wheel styles will require more cleaning effort.
From dead-on at either end the top-dropped Z4 has strong resemblance to a scaled-down version of the 6 Series and its roadster precursor, the Z8. Sections of the taillights look like horizontal light tubes and appear to ramp up like theater lights when the lights are switched on. Adaptive brake lights deliver more red light when you hit the brake pedal hard than when merely slowing mildly. The center brake light is midway between the rear window and the tail on the trunk lid where it will not interfere with rear vision but will be covered up by an inch of snow. A single side twin-exhaust outlet signals a 30i, while the 35i uses a single outlet on each side, a la Z8.
Although front-end shaping is the same, with BMW's trademark corona (programmable) daytime running lights for instant identification, trim varies by model. The 30i has black vanes in its grille and a silver slash across the outer lower grilles, while the 35i has matte silver grille vanes and perimeter frames for the outer grilles. While the Z4 is close to the ground the front overhang is shorter than many other sports cars and not prone to scraping at every speed bump or mild driveway entrance.
The Z4 is longer than the Audi TT and Mercedes-Benz SLK, shorter than the Porsche Boxster, but the difference is a few inches. In height and width, they are much closer, so exterior dimensions should not factor into purchase decisions.
The Z4 is now built in Regensburg, Germany. In BMW fashion, many systems on the Z4 have been proven in other recent BMW models, including the higher-output engine, transmissions, and suspension design.
There is no wind-blocker panel for between the headrests, as specified in early option sheets, though we have seen photos and it may become available through your dealer.
Cargo room is about average for the class, but better with the top up (10.9 cubic feet). On cars with Comfort Access you can, through the key fob, lift the stowed roof out of the way for easier loading and unloading.
The interior of the sDrive35is includes a thick-rimmed M leather steering wheel with gearshift paddles, an M driver's footrest, and sport seats. Gray-faced instrument dials have an sDrive35is designation. Additional interior features include the Anthracite BMW roof lining, M door sill strips, floor mats with colored piping and the sDrive35is designation, and M trim in Aluminum Carbon.
BMW labels this Z4 an expression of joy. We usually just smile, and the Z4 may well bring a smile to your face, so we'll go along for now. While the retractable top and added features have nudged it a bit closer to grand touring car than sports car it is still clearly aimed at those who enjoy driving.
Both inline sixes are smooth as an America's Cup boat hull right to redline, deliver a sonorous note, are 3.0 liters in capacity and there ends most similarity. The 30i engine is a very light, modern, rev-happy unit that brings 255 horsepower at 6600 rpm and 220 pound-feet of torque at 2600 rpm; it has more than enough power for any road and delivers it in linear fashion, its output rising commensurate with revs. This package is EPA-rated at 18/28 mpg with both the manual and the automatics, numbers we easily met or exceeded.
Although also displacing 3.0 liters, the 35i's is a different engine altogether. It uses two very small turbochargers to boost maximum horsepower to 300 at just 5800 rpm and more noticeably, increase torque by 80 pound-feet to 300 from just 1400 rpm through 5000. The extra muscle gets the 210-pound-heavier 35i to 60 mph a half-second quicker than the 30i and delivers plenty of power for street and track alike. It will wind to 7000 rpm but there's really no point with that abundance of torque, and while it's a superb engine it doesn't offer the emotional happiness the 30i does.
EPA numbers are 18/25 mpg with the manual transmission and 17/24 mpg with the dual-clutch seven-speed. With decent aerodynamic drag numbers, a relatively small frontal area, and an efficient driveline we managed almost 24 mpg in a manual-transmission model over some amusing roads and 38 mpg/72 mph on an 80-mile leg from 4,000 feet elevation down to 700.
The six-speed manuals, both of them, offer soft, progressive clutch take-up for smooth starts whether crawling in traffic or weekend autocrossing. Shift action is light, short and semi-notchy, rather like there's a rubber-edged metal gate hiding under the shift boot. Shifts are quick, clean, and error-free.
The 30i automatic is a conventional six-speed unit and goes about its business exactly as intended; it's not as quick as the manual but costs only in purchase price and not fuel economy.
However, the stronger engine in the 35i gets an optional seven-speed dual-clutch automatic from the M3. Don't let the name confuse you: It does have clutches but they are all controlled by the car, the only coordination required is engaging D and pressing the gas. Around town you will feel like it has a momentary delay between when you press the accelerator from a stop and when the car starts moving; the actions behind this are also why it doesn't creep in gear as much as a conventional automatic.
Pushbutton mode changes allow you to ratchet up the speed and intensity with which it shifts to the point where it is faster than the manual and makes a milliseconds-long burp from the exhaust pipes as it rips through the gears. It's also smart, doing things like dropping gears automatically (rev-matching the downshifts) if you hit the brakes hard to go into a corner, but it will shy away from gear changes mid-corner so it doesn't upset the balance of the car. There is also a launch control mode for ultimate acceleration but read the owner's manual cautions on this before you take the steps and disappear in a wisp of tire haze.
Since it has more power and weight, the 35i gets substantially larger brakes. Brake performance and feel is good across the range, and we had no brake issues at all charging downhill in 100-degree weather in a 30i; those who consider themselves racers may opt for the 35i's bigger parts. The 35i also has wider rear wheels and tires to cope with the added weight and power.
A 35i with Sport Package, dual-clutch gearbox and 19-inch wheels arguably makes the better track car in terms of outright performance, but we found the 30i with Sport Package the sweeter ride on a winding road where the lighter weight is felt, reactions and response seem more linear, and the whole effect is more pure sports car than race car.
Expect the sDrive35is, with its 335 horsepower and 332 pound-feet of torque, and the overboost function that provides temporary doses of 369 pound-feet, to be even more exhilarating when you step into the throttle. This promises to be a very quick roadster, indeed, and will deliver performance levels exceeded by only the most powerful, and expensive, supercars. For those who want the ultimate Z4, the sDrive35is will surely fill the bill.
Even on the standard run-flat tires (no spare) and optional Sport Package the Z4 rides commendably well. Part of this is good suspension tuning, part from the rigid structure it's mounted to, and part from the adaptive damping included in the Sport Package that allows for Normal, Sport, and Sport-plus settings.
Steering is electromechanical but you'd never tell by how well it communicates what the front tires are doing. Unlike many sports cars, in which it seems that heavy steering was a design requirement, the Z4 is light around town, weights up nicely with cornering force and reminds us somewhat of the Honda S2000. It can't really match the surgical detail of the Porsche Boxster, but nothing at this price, short of a Lotus, does.
With a low center of gravity and near-perfect weight distribution with occupants, the Z4's handling is exemplary. You'd need something considerably lighter, more stiffly sprung, and equipped with fatter or stickier tires to make notably faster progress. Like the Mazda RX-8 (a light two-door, four-seat, front-engine, rear-drive coupe), the Z4 is not only nicely balanced and goes where you point it, it does so with little drama and it's relatively easy to find where its limits are.
Putting the top down doesn't change the behavior at all because it's the lightest such assembly in the industry (aluminum panels), changes front/rear balance by only 0.3 percent, and puts the weight of the top closer to the ground. You could argue lowering the top costs some rigidity as the triangulation between windshield, floor, and trunk is gone, but there is no cowl shake and only the inside mirror vibrated a bit on poor road surfaces so characteristics don't change.
The one thing you do have to get used to, depending on whether you're looking at the road or the hood, is what your brain might interpret as a momentary delay between when you turn the wheel and when the car rotates and changes direction. Since you sit so far from the front axle and very near the rear axle, steering input tends to send the hood off to one side before you feel the rear tires join the party. It's a sensation the more driver-forward Boxster and TT don't offer, and it's much more muted in the softer SLK.
Among the competitors, the SLK also offers a folding hardtop, while the Audi TT and Porsche Boxster use folding cloth tops; they're perhaps not as quiet and sealed as a hardtop, and not as easy to see out of, but trunk space doesn't suffer as much when motoring top-down. The TTS has the foul-weather bonus of all-wheel drive and a nicely finished cabin, but not the same balance and precision finesse as the Z4. The Mercedes offers many similar amenities but is less a driver's car and more a small version of the SL luxury convertible. The Porsche Boxster has an even better driving precision and the power of the 35i with the driver's engagement of the 30i, but its tariff can rise even faster than that of the Z4.
The 2010 BMW Z4 sDrive30i ($46,000) comes with a 3.0-liter inline six-cylinder engine of 255 horsepower at 6600 rpm, 220 pound-feet of torque at 2600 rpm and a six-speed manual transmission; a six-speed sport automatic with shift paddles is optional ($1,375). It's delivered with faux leather leatherette upholstery, manual climate control, power retractable hardtop, heated power mirrors and rear window, six-way manual bucket seats, tilt/telescoping steering wheel, rain-sensing wipers, power windows and locks, trip computer and adaptive bi-Xenon headlamps. Options include brushed aluminum or ash wood trim ($500) and the Kansas leather upholstery ($1,250) from the sDrive35i.
The Z4 sDrive35i ($51,900) has a 3.0-liter inline-6 that delivers 300 horsepower at 5800 rpm and 300 pound-feet of torque from 1400 to 5000 rpm; it is a different engine than the 30i and employs twin turbochargers. A six-speed manual gearbox is standard and a seven-speed dual-clutch automated manual optional ($1,575). Other mechanical upgrades include larger brakes and wider rear tires and wheels. Cabin upgrades include standard leather upholstery, brushed aluminum trim or ash wood, and automatic dual-zone climate control. Kansas leather upholstery on the dash, visors, and door sills ($1,350) is optional, along with a 19-inch wheel upgrade to the Sport package ($1,200).
Options for the sDrive30i and sDrive35i include navigation ($2,100); Comfort Access ($500); Park Distance Control ($750); satellite radio ($350); smartphone integration ($150); anti-theft alarm ($400); and metallic paint ($550). The Cold Weather Package ($1,000) includes heated steering wheel and seats, storage pack, through-loading system, and headlight washers. The Premium Package includes auto-dimming mirrors, gate opener, power seats with lumbar and driver memory, ambient light package, BMW assist, and leather on the 30i. Premium Sound ($2,000) adds a six-disc DVD changer, hi-fi sound system, and iPod/USB adapter. The Sport Package adds 18-inch alloy wheels and run-flat performance tires, Adaptive M suspension, and sport seats; 19-inch wheels are also available. Exclusive Ivory white Nappa leather is available, along with anthracite wood trim.
The sDrive35is features an engine with increased intake air flow and increased boost pressure to deliver even more power. Its maximum output is 335 horsepower at 5800 rpm and 332 pound-feet of torque from 1500 to 4500 rpm. In addition, its engine management system includes an electronically-controlled overboost function which allows briefly increasing torque by another 37 pound-feet, for a temporary peak of 369 pound-feet and a significant increase in acceleration. While the sDrive35i will accelerate from 0 to 60 mph in 5.1 seconds, the sDrive35is will do it in 4.7 seconds.
The sDrive35is has the seven-speed dual-clutch transmission as standard equipment, with the programming tailored to complement the nature of the car and engine. The sDrive35is also features some M Sport upgrades, including M Aerodynamics and adaptive M Suspension, which combines a ride-height reduction of 10 millimeters with electronically-controlled shock absorbers to improve handling without compromising comfort. It also has special five-spoke 18-inch alloy wheels, with 19-inch wheels optionally available. Finally, it features aluminum trim bars in the outer air intakes, a rear bumper with accentuated surrounds on the tailpipes, and a rear diffuser finished on top in body color and below in a black textured surface.
Safety features for the Z4 include frontal airbags, head/thorax side airbags in the seats, active knee protection, roll hoops, electronic stability, traction and braking controls, and tire-pressure monitoring. The only option that might be considered safety related is the Park Distance Control.