50 Years of the BMW Isetta
Bubble car instead of boulevard cruiser
March 28, 2005 8:52 PM
Filed Under: BMW, Classics, German
Press Release
The presentation on 5th March 1955 was appropriate to the event. Without pomp and ceremony, but filled with quiet pride, the top management of BMW unveiled their latest product before the assembled press. In the opulent lakeside Hotel Bachmair in Rottach-Egern, the journalists were shown a two-seater, but one which was unlike any sports car. The configuration of the new BMW was something quite different. Fritz Fiedler, then BMW’s Head of Vehicle Development, summed it up in his opening speech: “With the BMW Isetta Motocoupé, the public are being offered an economical type of car and a concept that is quite novel in Germany.” Indeed, no vehicle like it had been seen before on German roads: a tiny, almost spherical car with windows all round – and a single door at the front.
Admittedly, the latest BMW hardly came as a surprise. The company had announced its new model back in the autumn of 1954, and six months prior to that the Isetta had been available for inspection for the first time at the factory in Milbertshofen. In the early 1950s, the Bayerische Motoren Werke were still suffering from the after-effects of the Second World War. True, in 1948 motorcycle production had been resumed with great success. Up until 1954 sales of the single- and twin-cylinder machines with shaft drive soared upwards. Nevertheless, it quickly became clear to the market strategists that the two-wheeler was only the first rung on the mobility ladder and the desire for a weatherproof vehicle was their customers’ prime consideration. With the big 501 Saloon, which had a pre-war six-cylinder engine under the bonnet, BMW was certainly offering a fast and luxurious car; but for a large part of the population it was several times too expensive. The company had no alternative to offer, since the resumption of car production after the war had been made extremely difficult by the loss of the Eisenach car plant. Production facilities as well as skilled staff had to be replaced. Not until the Frankfurt Motor Show in 1951 was the BMW 501 put on the road as the company’s first post-war car. The prestigious and extravagantly engineered saloon had even been improved by fitting it with the world’s first light-alloy eight-cylinder engine in time for the 1954 Geneva Motor Show, but the volume needed for profitable production could not be achieved.
1954 Turin Motor Show: BMW meets Iso.
At the beginning of 1954, shortly after the Board of BMW had proudly presented the new V8 on the shores of Lake Geneva, BMW’s main agent in Switzerland, C.A. Drenowatz, was visiting the Geneva Show when he discovered a “fully-faired motorcycle” called an Isetta and manufactured by the Italian firm Isomoto. He immediately reported his findings to the head of sales, Hanns Grewenig. Since BMW’s top management had already spent a lot of time thinking about a popular car that would represent the best possible value for money, they dispatched Eberhard Wolff, who headed the test division, to the Turin Motor Show which was held in late April and where Iso was again showing its Isetta to the public. There were two prime considerations: it was essential that the Isetta could be put into production a) quickly and b) at no great cost.
The first thing that struck one about the Isetta was its shape. Yet the “egg on wheels”, as the little vehicle was described right from the start, was remarkable not only for its unique profile, but also for its unusual technical features. For instance, the whole of the front end could be opened outwards – not even luxury saloons offered such a spacious method of boarding. The steering wheel and instrument panel were fixed to this door, which extended across the whole width of the car. A universal joint, which split the steering column a few centimetres above the floor panel, enabled one to move the steering column forward as well. Thus the driver and passenger merely had to clamber over the fixed foot pedals and could settle onto the two-seater bench without any contortions. Behind the seat was a generous space for the spare wheel and, if necessary, luggage. To the rear of the occupants puttered the heart of the little Italian job, a two-stroke engine with twin cylinders, which had a capacity of 236 cc and could deliver 9.5 horsepower.
BMW buys the name and the tooling along with it.
Wolff recognized that the simple and relatively easy-to-produce design of the microcar had exactly the potential that BMW was looking for. Even before the exhibition closed its doors, he got in touch with the head of Iso, Renzo Rivolta, who was already extremely interested in doing licensing deals. A partner with such a great name as BMW, moreover, seemed like a godsend. His offer was attractive: BMW could take over both the name and principal tooling for the bodywork. The BMW Board wasted little time and the then Technical Director, Kurt Donath, and Head of Development, Fritz Fiedler, drove to Milan to get down to brass tacks with Iso.
The Isetta: “It is deliberately not intended to be a saloon car…”
Almost exactly one year later, the BMW Isetta was launched. Many visual and technical details of the Italian original had been modified and improved by BMW. A first glance showed the bodywork had been altered by having detached headlights fitted at the top of the front-opening door instead of the bottom, and by giving it a new engine cover. In practical terms, Fritz Fiedler had no difficulty in justifying BMW’s bold decision in favour of the Isetta to the assembled trade journalists. In order to bring down the retail price, he said, many manufacturers would previously have tried to save costs in two ways: “Some of them want to achieve this objective by a nitpicking reduction of all the dimensions, following the simplistic calculation made by a lot of people that a hundredweight of car costs so much. The other method of getting the price down is crudeness. In extreme cases I picture the design as a tubular rod, to which some road wheels are attached which are steered by handlebars.” This kind of steering – others called it a joystick – was found, for example, in the Messerschmitt “cabin scooter”. “Between these two extremes,” Fiedler went on, “we now have the BMW Isetta. It is deliberately not intended to be a saloon car, but it is more than something to get you from A to B. It gives its occupants complete protection against the weather; you can get into it with greater ease than many a big car, and it can be driven with such supreme safety that even inept drivers put neither themselves nor others at risk.”
The Isetta’s five trump cards.
Fiedler summed up the advantages of the Isetta in five bullet points:
“1. The cost of the bodywork is decisively influenced by the number of doors. You can get by with one door. The door is not hung in the outer skin of the bodywork, but stands proud of the front end and hence is accident-proof.
2. Three wheels may be cheaper, but they are not nearly as good as four. Putting the drive through a single rear wheel overstrains it. That’s why we opted for two rear wheels. The narrow wheelbase saves us fitting a differential and means that one brake is enough.
3. It has been possible to locate the engine in front of the rear axle, achieving an ideal weight distribution.
4. Thanks to a transverse double cardan shaft, the suspension of the axle and the engine is independent.
5. The egglike shape of the body is taken from nature. It requires least expenditure on materials to enclose a given interior space.”
This catalogue contained numerous BMW ground rules which still apply today – passive and active safety, optimum distribution of axle weight, driving comfort. And there was something else in the new “Motocoupé” – a BMW engine. The original noisy and underpowered two-stroke had already been available at the time of the negotiations between the BMW Board and Renzo Rivolta. If the bodywork was to be bought in, at least BMW could supply its own power unit. And anyway, in Munich there was a proven, reliable and perfectly suited power source: the single-cylinder engine of the BMW R25/3 motorcycle.
A tried and tested motorcycle engine for the new Motocoupé: the single-cylinder 250.
This vehicle set new standards in its class: from a cylinder capacity of 245 cc the single-cylinder generated 12 horsepower at 5,800 rpm. Its construction was as robust as it was simple. The crankcase and cylinder were made of cast iron, the cylinder head of aluminium. However, the head was rotated by 180 degrees compared with the motorcycle engine. The twin-bearing crankshaft was also different in the Isetta power unit, being larger and featuring reinforced bearings. One of the reasons for this was the heavy Dynastart unit which combined the dynamo and self-starter. The laterally located camshaft was driven by a roller chain, and transmitted its control impulses via pushrods into the cylinder head, where the overhead V-shaped valves were activated by rocker arms. The fuel mixture was provided by a Bing sliding carburettor. In addition to further changes of detail, the BMW engineers enlarged the sump for installation in the car and cooled the engine by means of a radial fan.
Economic motoring: top speed of 85 km/h (53 mph) and around 80 mpg.
To quote from a press release at the time of the launch: the engine “gives the BMW Isetta excellent acceleration, with help from the well-chosen ratios in its four-speed gearbox, which also has a claw shift and reverse gear. Gradients of up to 32% can be surmounted with ease. Fuel consumption is as little as 3.8l/100 km (approx. 80 mpg). The maximum speed of 85 km/h (53 mph) can be exploited without anxiety in view of the hydraulic brakes on all four wheels.” With this braking system the Isetta set new standards in the “bubble car” class, since the competition were still fitting cable brakes as standard. Incidentally, the braking arrangement was as follows: each of the front and rear wheels had a drum brake. Admittedly, only the left rear drum was connected to the hydraulic circuit of the service brake. The right-hand drum was connected by a cable to the handbrake lever, which stuck up vertically by the driver’s foot. And in the mid-1950s, by no means every car could boast four forward gears. With a torque of only 14.2 Newton metres at 4,500 revs those gears were sorely needed, even though with a full tank the Isetta only tipped the scales at 360 kg.
Safe roadholding despite a short rear axle.
Initially the wheelbase layout aroused deep suspicion. The two front wheels were mounted at each corner, 120 cm apart, whereas the two rear wheels were tucked in centrally with a track of just 52 cm, making the “darning ball”, as the diminutive car was sometimes dubbed, look like a three-wheeler. The power train from the four-speed gearbox to these two wheels was unusual enough: fixed to the gearbox output drive was something called a Hardy disc, which was a cardan joint made of rubber. On the other side of it was a cardan shaft, and finally a second Hardy disc, which in turn was located at the entrance to a chain case. A duplex chain running in an oil bath led finally to a rigid shaft, at each end of which were the two rear wheels. Thanks to this elaborate power transfer, the engine-gearbox unit was both free of tension and well soundproofed in its linkage to the rear axle. This paid off in terms of a surprisingly comfortable drive and very well-balanced roadholding.
Yet at this point no journalist, let alone a customer, had ever driven the Isetta. Development boss Fritz Fiedler anticipated the scepticism and tackled it head on: “There will probably be heated arguments among experts and laymen about the rigid, uncompensated rear axle with a track significantly narrower than the front one. But there is nothing new about this. These vehicles are said to perform particularly well in hill-climbs on bad and winding roads. We found exactly the same thing in our test drives. No-one who hasn’t seen it for himself can believe how well and how safely this vehicle handles.”
A succès d’estime at the Mille Miglia.
And he was able to prove it too. Back in 1954 the Isetta had taken part in the Mille Miglia – and earned its spurs: over a distance of 1,000 miles the drivers achieved an average speed of over 70 km/h (43 mph). In view of its maximum speed, which was just 15 km/h higher, this was an almost incredible figure. There is no doubt that this was helped by the fact that the front-wheel mountings and suspension moved with the steering, which meant that the steering geometry remained unaltered even when the car tilted and rebounded – the Isetta’s roadholding was exemplary.
What lay behind this was the overall design concept consisting of an all-steel body which rested on a trapezoidal tubular steel frame. The front wheels were mounted individually on longitudinal cranks whose movement was checked by coil springs and frictional shock absorbers. The rear axle was fixed to the body by two quarter-ellipse leaf springs and two telescopic shock absorbers.
Parking nose-in to the kerb.
Admittedly it was in towns that the bubble car, 2.28 metres long by 1.38 metres wide, scored the highest points. Fritz Fiedler gave the journalists the perfect tip for parking: “You drive into the parking space facing the kerb, park the car and get out at the front, straight on to the pavement. After nearly 25 years, BMW might pull out their old slogan again: Bigger inside than outside.” Thanks to the overall length of precisely 2 metres, 28 centimetres and 5 millimetres, even the meter maids turned a blind eye to this style of parking.
Plenty of elbow room inside.
Indeed the Isetta did offer a uniquely spacious driving experience. To quote again from the press release announcing the Motocoupé: “Large windows made of shatter-proof Plexiglas allow an open view in all directions. There are handles to open the sun-roof as well as the two quarter-lights that give draught-free ventilation. Two adults and a child can sit comfortably on the bench seat, with a full width of 1.18 metres, which can be adjusted forwards or backwards. The space between the seat and the front door is 70 cm, giving the occupants ample room for their legs and feet. Any restriction of the driver’s movements is avoided, not least by the fact that the gear lever is located on the left to save space and the remaining manual controls are conveniently grouped on the steering column.” The steering column was between the driver’s legs, to the left of it was the clutch pedal, and to the right the brake and accelerator. “Thanks to the swivelling quarter-lights, the sun-roof and the fan-heater, it is possible in all weathers and in any season to cover the longest distances in a comfortable environment.” Some people took this literally: it is on record that a married couple drove an Isetta from Sicily to Sweden in 62 hours.
Safe and considerate: a door with a knuckle-joint lock.
The characteristic feature of the Isetta, which brought it the nickname “Christmas car” (“Open wide the door…”), was incidentally not intended purely for the comfort of passengers getting in, but also designed to have environmental benefits. Development boss Fritz Fiedler argued it this way: “We even chose a special design for the door lock. No longer will people have to slam the door shut with a loud bang – the nocturnal terror of anyone living near a pub – because the door is closed silently and safely with a kind of knuckle-joint lock, which goes over a dead point. At the same time this prevents the door, if not properly closed, from swinging open when the brakes are applied.”
On that day, 5th March 1955, a grand total of two Isettas were available to journalists for them to put these promises to the test. This they did in good measure – and were delighted. They praised the “successful synthesis of motorcycle/scooter and four-seater car” and paid tribute to the unique concept of the Motocoupé. The Isetta was clearly distinct from the competition. In Germany alone more than 20 manufacturers were offering an enormous variety of bubble cars and small cars for all tastes and almost every purse. At that time necessity mated with invention to produce some strange offspring. Some had the occupants sitting one behind the other, tandem-style, and some even back to back.
Value for money: six months’ work for an Isetta.
The Isetta was a hit. BMW had been right about its “ideal solution of the motoring problem for everyone who needs a nippy and manoeuvrable vehicle with low running costs and no difficulties in parking or garaging. This means wage- and salary-earners going to work, doctors, salesmen, skilled tradespeople, representatives travelling for big firms, the self-employed and, not least, the lady of the house when her husband has taken the ‘big car’ out.” Apart from its technical qualities, a point in favour of the Motocoupé was the modest list price asked by BMW: just 2,550 deutschmarks. Good value, but not cheap. In those days a German worker earned an average of DM 90 per week, so he would have to work a good six months to buy an Isetta. The obligatory third-party insurance cost DM 95, and the taxman demanded an annual road tax of DM 44 for the “smooch-ball” – or “less than a dachshund in the city”, as the advertisements assured people.
1955: demand exceeds supply.
BMW had set a production target for the year 1955 of 11,200 Isettas; in the event the figure was considerably higher – but it still did not meet the demand. In the company’s annual report the Board proudly announced: “In the year 1955 the West German vehicle industry was able to increase production by a third. We shared fully in this expansion. Total sales from our plant in Munich-Milbertshofen rose by 46% to DM 138,000,000. The decline in our motorcycle business, which we had already indicated in previous years, has been halted by the timely introduction of the BMW Isetta Motocoupé, though the launch costs are being charged to the year just ended. With the increase in the Isetta’s production volume, the breakeven point was passed as early as the beginning of 1956 and so it was already contributing to the profitability of the factory. The BMW Isetta’s extraordinarily favourable reception in the market led to a rapid increase in output. Overall, since the start of production in April, which then rose to a volume of 2,000 units per month, no less than 12,911 units had been manufactured and sold by the end of 1955.” BMW produced as many Motocoupés as was physically possible – sometimes under the most adverse conditions. For example, workers would be assembling the bubble cars on the production line while, a few steps away, bricklayers were still busy repairing the war-damaged workshops. Even so, purchasers usually had to wait a month before they could take delivery of the Isetta they had ordered.
The finest car under 4,000 deutschmarks: the Isetta.
It soon turned out that the overwhelming majority of proud Motocoupé drivers were very satisfied with their choice: “And if anyone has had the slightest thing to complain about, up to now he has always been torn to pieces in an avalanche of readers’ letters,” reported the journalists in a trade magazine of the day, “Rollermobil und Kleinwagen”. The quirky profile of the Italian-born creation was even considered chic. So it was that in summer 1955, at the Bad Harzburg motor rally, the Isetta won the beauty contest in the under DM 4,000 price category.
By the middle of 1956, however, it seemed that the sharp rise was already being followed by an equally steep drop. The blame for this lay with two rumours. According to one, BMW’s competitors were planning new small cars – larger but just as good value. This was unsettling for potential Isetta buyers: BMW had in any case raised the Isetta’s price to DM 2,750, and the market reacted by holding on to their wallets. The second rumour did not improve things either: it was that BMW intended to cease production. In June the company went out of their way to deny this in the press: “A rumour has recently surfaced to the effect that manufacture of the BMW Isetta is going to be closed down due to the expiry of the licence and the appearance of a new and larger car. Exactly the opposite is true. The BMW Isetta assembly plant in Munich is currently being considerably enlarged, in order to increase still further the current daily output of 200 vehicles.”
More performance: the Isetta with a 300 cc engine.
The customers accepted the statement, the competing cars failed to materialize and sales picked up again. At the same time, in 1956, work began on expanding the range: the engineers enlarged the single cylinder to a 72 mm bore and 73 mm stroke, which yielded a cubic capacity of exactly 298, and at the same time they raised the compression ratio from 6.8 to 7.0:1. In this way the engine now generated 13 horsepower at 5,200 rpm, and the torque rose to 18.4 Newton metres at 4,600 revs. True, the maximum speed remained at 85 km/h, yet there was a marked increase in flexibility, chiefly noticeable on gradients.
In addition to the desire for more performance, a part in the choice of this engine variant was played by factors which lay quite outside BMW’s purview. Firstly, it was then still possible to drive the 250 cc Isetta with the old Class IV driving licence. Quite a number of Isettas were lovingly maintained by their owners for years and even decades, precisely because they possessed no other licence. On the other hand, from 1956 onwards, first-time drivers had to pass the test for Class III if they wanted to drive a car. True, the Class IV licence continued to be issued, but it was only valid for small motorcycles. A second, similar reason for fitting the larger engine was the prevailing tax regime. The 250 cc engine did not take full advantage of the tax class, which then went up to 300 cc.
1956: export version with improved fittings and technology.
In autumn 1956, BMW went on to introduce export versions of both variants. Externally they differed from the standard models by having a full-width front bumper, large sliding side windows, a collapsible soft top and chrome drip rails. But underneath the body even more had changed. In order to improve the ride, the swinging arm on the front axle had been lengthened, the springs enlarged and the frictional shock absorbers replaced by modern telescopic ones. In parallel with this the rear axle suspension was also new and adjusted for a softer ride. Both the earlier model, now called the Isetta Standard 57, and the new Isetta Export 57 were available with either the 250 cc or the 300 cc engine. Linked with the launch of the upgraded variant was a reduction in the price of the basic model to DM 2,490, whereas the export version cost DM 2,750.
The “Export” label was indeed entirely justified: as early as 1955, the Isetta’s resounding success in Germany was followed by a growing interest in the little bubble car not only in continental Europe but also overseas. BMW were not about to let this business slip away. Among others, export versions with the designation “Overseas model” and “USA model” were developed. The former was essentially distinguished by additional ventilation for the occupants and power unit as well as so-called “tropic-proof enhancements to all body, chassis and engine components”. This boiled down to “protection from attack by fungus and termites”. On request, BMW additionally offered overseas customers several special options: right-hand instead of left-hand drive, a cabriolet hood and a removable platform for a 200-kilogram payload, as well as strengthened suspension. These extras were so attractive that they were immediately offered to German customers as well.
Bubble car instead of boulevard cruiser: 12,787 Isettas for the USA.
BMW also put together a special Isetta package for prospective buyers in the USA, mainly with changes necessary to meet legal requirements in that country. Thus the American version was given parking and side lights, different headlights, more powerful winkers and larger rear lights. There were also fold-out side windows and modified ventilation. If required, US buyers could also order a cabriolet roof and twin windscreen wipers instead of one. By September the first Isettas were on the high seas bound for the land of gas-guzzling limos, and by the end of the year some 1,200 units had been shipped out. Over its whole production life the Isetta found 12,787 buyers in the USA.
Even in 1957, a good two years after the launch of the Isetta, BMW was still garnering a great deal of praise for the bubble car. For example, one leading motor trade commentator of the day wrote of the 300 cc export model: “It is far easier to follow well-trodden paths and build a medium-powered car on proven lines for the well-heeled citizen than a runabout that will put no greater strain on the wallet of the man in the street than a motorcycle and sidecar might have done up to now.” Finally, he wrote of the Isetta: “This unconventional vehicle represents an unusually apt way of performing the tasks it is intended for, and a lot of hard development work has yielded something of great practical value.” In that year BMW built nearly 40,000 units – the greatest annual volume in the Isetta’s production history. Along with the Goggomobil, the “smooch-ball” had become the most successful vehicle of its kind in Germany, and many local me-too equivalents of the BMW Isetta appeared in Britain, Spain and even Brazil.
Competition from under the same roof: the BMW 600 and BMW 700.
Along with Germany’s Economic Miracle, by the end of the 1950s the demands of car buyers began to grow. The spartan microcars had passed their zenith, and customers were demanding proper automobiles. In 1957 BMW initially reacted by launching the 600, an Isetta with a longer wheelbase and a rear-mounted twin-cylinder horizontally opposed engine. By 1958 the tubby four-seater with its 19.5 bhp engine had ousted the Isetta from its place as the company’s number one revenue earner. With sales worth 75.5 million marks, the BMW 600 accounted for 39 percent of BMW’s turnover; the Isetta only managed DM 53 million or 27 percent. However, in 1959 the BMW 600 was replaced by a distinctly more modern design whose bodywork was created for the first time using a monocoque construction method: the BMW 700.
The two new product lines were now eating into the Isetta’s sales. In 1958 barely 22,000 Motocoupés rolled off the Munich production line, and a year later the figure was down to around 20,000. But as the BMW annual report stated: “The decline in domestic sales of the Isetta is balanced by a significant rise in shipments of CKD Isetta kits for assembly abroad.” Whereas in 1958 a mere 825 Motocoupé kits had been shipped worldwide, in 1959 the figure was 6,900.
The end of an era: production closes down in May 1962.
Nonetheless, the “egg on wheels” put up a brave fight against competition that was growing ever greater and more modern. This was chiefly due to its attractive price combined with high quality. At DM 2,650 for the 250 cc Isetta in 1960 and DM 2,710 for the 300 cc version, the little car was almost unbeatable on price. Even its tough competitor, the Goggomobil, was asking no less than DM 2,947 for its basic T250 model. In any case, the price review in a motor trade magazine in 1960 noted on the Isetta: “Price supplement for heater: DM 45, sliding roof is standard” – in those days it was the only German car that offered this extra on all production models. Only one vehicle in that list was even cheaper than the Isetta: the Messerschmitt KR 200 cabin scooter, at DM 2,395, heater included. But it didn’t help. In 1961 a motoring magazine put it like this: “However you look at the Isetta, it has had its day.” A year later BMW ceased production of the Isetta. A total of 161,728 units had been built. The report by the Board for 1962 noted succinctly: “After running down parts stocks, manufacture of the Isetta came to an end in May as planned.”
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