Design to Reality: the Z4 Roadster

Z4 concept sketch

This is where the Z4 began. Although the sketch has the usual exaggeration of most concept designs, the actual vehicle is a whole lot closer to this rendering than is usually the case.

Z4 Roadster

While many roadsters, Anders Warming says, use an overall cylindrical shape, the Z4 is characterized by twisting shapes. Note the two beltlines, with the lower implying the classic shape of a roadster.

Z4 Interior

The Z4 is engineered with the latest in technology—from electric steering to run-flat tires to a DVD-based navigation system. Note how the interior is not only functional but reflects the shapes of the vehicle exterior.

When Anders Warming was growing up in Denmark, he was sometimes asked by teachers what he wanted to be when he was older. And he told them that he wanted to become a car designer. The response was something of a blank look. After all, the Danish car industry doesn’t really exist. According to the CIA’s The World Factbook (if those guys don’t know what’s going on in the world, then who does?), Denmark’s industries consist of “food processing, machinery and equipment, textiles and clothing, chemical products, electronics, construction, furniture, and other wood products, shipbuilding, windmills.” Not cars. Not the things that Warming wanted to design. But he kept sketching. Kept at it despite the curious looks he must have received from teachers and the like. In time he made his way to the campus that Art Center College of Design had established in Switzerland. And then moved to the main campus in Pasadena. Upon receiving his degree, he went to work for Designworks/USA (Newbury Park, CA), which is part of the BMW Group. Warming is now the creative director of Automotive Design there.

During the summer of ‘98, Warming, who is always sketching when he has the opportunity, created a sketch for a car. Many sketches for cars as compared to real cars tend to look exaggerated and cartoony. Often, when you compare a sketch to the actual engineered-and-manufactured product, the points of correlation are difficult to discern (“Ah, they both have tires. . .but the wheels on that sketch are enormous.”).

However, the sketch that Warming did and the production version of the BMW Z4 roadster, which is now being manufactured by BMW Manufacturing Corp. (Spartanburg, SC), are easily identifiable as being one and the same. No, this has nothing to do with Warming being reticent when it came to his sketch. There’s the long hood and high cowl. A long wheelbase and low overhang. The driver is back and low. There are twisting planes and numerous crowns on the surface.

The Z4 doesn’t look anything like anything else. To be sure, there are various and sundry cues that one might identify from BMW roadsters of days gone by (e.g., the 315/1 and 319/1 from 1935; the 507 of 1956). And Warming admits that there may be some influences there that he wasn’t consciously aware of (e.g., he says that some people have told him that the round rear taillights are reminiscent of the BMW 2002). But he makes two points:

  • We wanted to make a clear statement.”
  • We didn’t want to design the Z3, Mark II.” (The Z4 is replacing the Z3, which went out of production on 28 June ‘02).

It is important to note the plural pronoun, the “we.” Warming is insistent that it isn’t “his” car. It is BMW’s car. He points out that there were plenty of designers, engineers, and manufacturing people involved in evolving the Z4 from being that sketch to a product that is currently being produced in Spartanburg on a two-shift schedule, at a rate of 230 per day.

The sheet metal (including an aluminum hood, which is said to be the largest single piece of aluminum made for a BMW product) on the Z4 is truly three dimensional, far more than traditional designs that Warmer says tend to be based primarily on cylindrical shapes. The Z4 has what he describes as “constant twists.” Asked whether the manufacturing people who would be responsible for stamping the steel body panels didn’t tell the designers involved that they were a little. . .well, not clear thinking, Warming responds that the people at BMW understand what it takes to make a BMW—which is to say that the manufacturing people are also with the program.

Looked at from the side view, there are two beltlines. One, starting at the headlight, forms a curve (upward over the fender area, downward along the door, then back up and down on the rear quarter) that is said to be reminiscent of the beltline of a classic roadster. The other beltline is functional; it is along the cockpit ledge. In addition to which there are various transitions from concave to convex on the surface, most notably in the diagonal line that is essentially a continuation of the angle of the A-pillar. Viewed from overhead, there is a wide front area that tapers back toward the cockpit, then widens again toward the trunk (think of something in the character of a Coke bottle). The decklid is designed so that the top, rear surface forms an integrated spoiler. Warming explains that he wanted a design that was functional without the need to add something extraneous.

Warming says that there is a metaphor of design at BMW: bookends. The 7 Series is at one end; the Z4 is the other. Warming suggests that as time goes on, people may be surprised at the designs they’ll be adding to the library of vehicles in between.


What Are They Thinking?

According to Ed Robinson, executive vice president, Operations, BMW North America, the roadster market is down 36%. Key Z4 competitors including the Audi TT and the Mercedes SLK are both down. Yet here’s BMW with a new vehicle.


  1. This is an emotional market, looking for new entries.” Consequently, he thinks that the roadster customer will be drawn to the Z4. (According the Hennie Chung, Z4 product manager, the Z4 is a “reward vehicle, the second or third vehicle in a garage.” Clearly, then, the roadster market is not one that’s largely driven by people in search of utility.)
  2. “We caused part of that down.”

That is, by stopping production of the Z3 in June, there were 6,000 fewer roadsters built than there would otherwise have been on the market.


Under the Aluminum Hood

The Z4 uses the in-line six-cylinder M54 engine that’s powering the 3 Series. There are two versions: the 2.5-liter, which provides 184 hp @ 6,000 rpm and 175 lb-ft of torque @ 3,500 rpm; the 3.0-liter, which provides 225 hp @ 5,900 rpm and 214 lb-ft of torque @ 3,500 rpm. The all-aluminum engines feature dual overhead cams and four valves per cylinder. There’s variable valve timing. An electronic throttle system—a.k.a., drive-by-wire—is utilized. (Speaking of drive-by-wire: there is also an electric power steering system used that replaces the conventional hydraulic pump with an electric servomotor. In other words, steer-by-wire.)

There are four gearboxes available. The standard in the 2.5i model is a five-speed manual; a new six-speed manual is standard in the 3.0i. Both models can be fitted with the automatic five-speed steptronic, which permits manual shifting. Starting in April ’03, there will be a sequential manual gearbox (SMG); this six-speed manual can either operate in an automated mode (put it in D3) or can be manually shifted via either the shift levers of the F1-racing-like shift paddles on the steering wheel. 

Selected Specs
Wheelbase:......................98.2 in
Length:.........................161.1 in
Width:............................70.1 in
Heights (top up):..............50.1 in
Drag Coefficient (top up):... .35 in

Base Price (including destination charges)