Classics

Testing the physics of convertible driving: the BMW Z1

No other model had such vertical-sliding doors, and few other sports cars could corner at such speeds. Launched in 1988, the BMW Z1 was a roadster that featured innovative high-tech and spoiler-free aerodynamics coupled with typical BMW six-cylinder power.

By
Jan Wilms

There was once a time when people jokingly referred to the Bavarian Motor Works as the Bavarian Roadster Works. Many fans of the vintage models of yesteryear will no doubt have fond memories of the lightweight, open-topped BMW 315/1 and BMW 319/1 sports cars, and of course the BMW 328 Roadster, which established the brand’s DNA back in the 1930s. But in truth the systematic focus on pure driving pleasure developed during this period still remains a feature of every BMW to this day. It is found in its most spectacular form, of course, in the direct successors to the first roadster generation, the BMW 507 Roadster dream car or the current BMW Z4. And in the BMW Z1 – a one-of-a-kind model that elevated driving pleasure to an even loftier level and was packed full of technological innovations.

One such feature was the self-supporting skeletal frame, previously used predominantly in monocoque form in motor sport. Then there were the innovative materials used, including a body made from recyclable thermoplastic panels, the elasticity of which was capable of absorbing minor impacts. As for the drive system, the car was fitted with a tried and trusted power unit, the 170 hp, 2.5-litre straight-six engine from the BMW 325i.

Fun factor vertically retractable doors

The Z1 largely owed its cult status to the electromechanical sliding doors that retracted vertically into the bodywork. This unique door design not only gave the car a futuristic appeal, it also minimised the distance between the driver and the road. The go-kart-like driving experience was the real deal – but no other regular everyday car could hold a candle to the Z1 when it came to the breezy thrill of taking the physics of driving to the limit. And the great thing about it was this: to put a smile on your face as broad as the BMW Z1’s distinctively generous footprint, you didn’t need to floor it and race from 0 to 100 in under eight seconds or even push the engine to its top speed of 227 km/h. All it took was a gentle, winding country road.

The Z1 owed its cult status largely to the electromechanical sliding doors that retracted vertically into the bodywork. This unique door design not only gave the car a futuristic appeal, it also minimised the distance between the driver and the road.

The BMW Z1 was conceived entirely with driving pleasure in mind. The interior and instruments were appropriately functional in design. An on-board computer was not available even as an optional extra.

Another innovative feature was the ingenious interplay between the car’s front mid-engine design and the chassis. Since the engine was mounted behind the front axle, and the 5-speed transmission drove the rear axle using the transaxle principle, the design achieved an optimum axle load distribution of 49:51. While the spring-strut front axle was borrowed from the BMW 3 Series, an all-new multi-link Z-axle was used at the rear to provide exceptional directional stability. The cumulative result of these measures was that the BMW Z1 had no need for power steering. Moreover, it boasted the highest lateral acceleration (up to 1 g) of any comparable car and even left sporting icons such as the Porsche 911 Turbo and the Ferrari 328 GTB trailing in its wake when it came to cornering.

The new kids at BMW Technik GmbH

The origins of the BMW Z1 were also cutting-edge. It was the first concept vehicle created by BMW Technik GmbH, founded in 1985 as an independent think-tank outside of the day-to-day workings of the parent company. BMW Technik’s job was to come up with the cars and innovations that others might only dream of. A revolutionary lightweight roadster, for example, that could use its state-of-the-art technology to create an unforgettably sensual experience for the driver. The new kids from BMW Technik also demonstrated in the Z1 something that is now universally accepted: that to slice through a headwind in a sleek, open-topped machine is the ultimate four-wheeled driving experience – at least for anyone seeking true driving pleasure.

A virtually series-ready prototype of the Z1 was unveiled at the IAA Frankfurt Motor Show in 1987; the production version was presented at the Paris Salon the following year. It was equipped with virtually every innovative feature from the prototype – which was anything but the norm. The motoring press talked of a “cultural revolution,” a “leap into the future,” and summed up the model’s features as “avant-garde,” coining the term “jet-zet” (a play on words of the series letter “Z” and “jet set”). The small production run of hand-built units justified the high price tag of 83,000 German marks (at the time almost 30,000 pounds sterling).

While the spring-strut front axle of the BMW Z1 was borrowed from the BMW 3 Series, an all-new multi-link Z-axle was used at the rear to provide exceptional directional stability.

The BMW Z1 was packed full of technological innovations. These included the self-supporting skeletal frame, used predominantly in monocoque form in motor sport. Then there were the innovative materials, including a body made from recyclable, thermoplastic panels, the elasticity of which was capable of absorbing minor impacts.

The BMW Z1 was packed full of technological innovations. These included the self-supporting skeletal frame, used predominantly in monocoque form in motor sport. Then there were the innovative materials, including a body made from recyclable, thermoplastic panels, the elasticity of which was capable of absorbing minor impacts.

Z1 in Dream Black, Top Red or Fun Yellow

Dream Black, Fun Yellow, Nature Green and Top Red – the distinctive colour designations alone heralded the imminent arrival of garish 1990s pop hedonism. On the other hand, the rest of the design adhered to traditional roadster driving philosophy and focused solely on the essentials. The BMW kidney grille, air intakes and headlights were almost rectangular in design. The front was the thin end of a high-tech wedge that scooped air with minimum resistance over the elongated bonnet towards the rear. The smooth underbody also used the wind to reduce rear axle lift substantially, with a motorsports diffuser generating additional downforce as speed increased.

Discreetly flared wings hinted at the roadster’s power, despite its almost dainty appearance – particularly with the side elements retracted, allowing easy entry and exit over the sills. And while the rollover bar was neatly integrated into the upper edge of the windscreen frame as a tube linking the two A pillars, the wing mirrors were moved up to the centre of the A pillars – making the Z1 equally avant-garde in terms of vehicle safety.

Spoiler-free aerodynamics

The result of this practical form language was outstanding aerodynamic performance – with an open-topped cd value of 0.43 without the need for aerodynamic spoilers or wings. And at the speeds the car was capable of, the driver naturally required exceptional sports seats, specially developed for the BMW Z1. Less spectacular perhaps was the rest of the interior and instrument panel, which in keeping with the overall concept was appropriately functional. An on-board computer was not available even as an option.

By 1991 the BMW Z1 had sold 8,000 units. With its unique profile, this was clearly never going to be a high-volume model. It was not the sort of car that John or Jane Doe would drive away from a dealer’s yard packed with the usual extras. It was a roadster for the driver with a genuine passion for auto dynamics, someone willing to sacrifice a little comfort for pure driving pleasure.

This rare roadster was created for drivers with a genuine passion for auto dynamics, people willing to sacrifice a little comfort in exchange for pure driving pleasure – with the possible exception of the superlative sports seats specially developed for the BMW Z1.

07/14/2017