The evolution of the steering wheel, a la Mercedes-Benz

Mercedes-Benz has teased the world with snippets of the new E-Class and among the various modern touches the German carmaker has made, one path-breaking technology stands out: the capacitive steering wheel. Mercedes-Benz says the steering wheel in its new E-Class will contain a two-zone sensor mat to detect the driver's hands gripping the steering wheel (which differs from previous tech, which depended on the movement of the wheel itself), and also includes touch sensitive buttons on the spokes, also designed to work with digital signals.

However, the first step towards the modern Mercedes-Benz steering wheel was taken 120 years ago by the then Daimler Motoren Gesellschaft (Daimler Motors Corporation) when the brand switched from a simple steering crank or steering rod to the significantly more functional, not to mention intuitive, steering wheel. This was the proverbial first step which has led to the development of today’s high-tech command centre, enabling countless drivers to not only steer their vehicles precisely and comfortably, but also operate numerous comfort and assistance systems.

When it comes to the steering wheel, developers and designers work hand in hand – and focus on perfecting every detail. For example, every millimetre of a circuit board determines how elegantly the surface can be designed, which goes a long way in perfecting the haptics, or user feedback.

“Steering wheel design is a world of its own and a very special challenge that is often underestimated,” says Hans-Peter Wunderlich, creative director, interior design at Mercedes-Benz, who has been designing steering wheels for around 20 years.

“Besides the seat, the steering wheel is the only component in the vehicle with which we have intensive physical contact. The fingertips feel little things that we normally don’t notice. If an unevenness is disturbing or the steering wheel does not fit snugly in our hands, we don’t like it. This haptic sensation is sent to the brain as feedback and determines whether or not we like the car.”

So now that we know the importance of the steering wheel, without further ado, let’s dive into its history, starting with...

No steering wheel at all

Yes! The first automobile in the world, Carl Benz’ 1886 Patent Motorwagen (motor car), was built with the aesthetics of a horseless carriage, just like the Stahlradwagen (steel wheeled car) designed by Gottlieb Daimler and Wilhelm Maybach in 1889, which meant neither of them had a steering wheel. They did, however, have a simple steering lever or steering crank which mimicked the operation of the crank used by carriage drivers, pulling on the right or left rein to direct the horses in the desired direction.

The steering wheel debuts at the world’s first automobile race

French engineer Alfred Vacheron is widely considered the inventor of the steering wheel. For the world’s first automobile race – the approximately 200km Paris to Rouen race in July 1894 – he installed a steering wheel instead of the usual steering lever in his Panhard & Levassor car, which was powered by a Daimler engine. He achieved his goal – better control – as the steering movement of the front wheels could be more evenly and precisely distributed over several turns of the steering column from a neutral central position until it stopped or ‘locked,’ thus also allowing higher driving speeds. Now, although the Frenchman placed only 11th, the steering wheel prevailed.

The Mercedes 35 PS and the Simplex

On April 2, 1900, Daimler-Motoren-Gesellschaft decided to call its automobiles Mercedes, after the daughter of Emil Jellinek. The Austrian businessman, who lived in Nice, and both traded in Daimler vehicles as well as registered them for racing events.

The first vehicle with this melodious Spanish name – the Mercedes 35 PS – caused a sensation at the Nice race week as early as March 1901. A distinguishing feature of this car was that not only did it have a steering wheel, but in this case the steering column was tilted, which made it much easier to operate. Nevertheless, every steering movement required a great deal of effort.

In the Mercedes Simplex (latin for 'simple') introduced in 1902, there were additional levers on the steering wheel which had to be used to regulate essential engine functions such as ignition timing and air/fuel mixture.

The 1920s to 40s: a large steering wheel with horn ring

While the levers for the manual adjustment of the fuel mixture and ignition gradually became redundant courtesy the improvements to automotive techology, an additional function from the early days of the car has persisted till date: the horn. The simplest form of car-to-car/pedestrian communication began with a bulb horn mounted on the steering wheel rim, followed by the klaxon horn button, consisting of a spring-steel diaphragm with a rivet mounted within the steering wheel hub. The horn ring on the steering wheel spokes made its debut in the 1920s, and was standard until the 1970s, becoming increasingly more intricate.

In 1949, the horn ring also took over the function of actuating the turn signals or indicators, a common feature in cars till the mid-1950s. To indicate a turn, the ring was simply twisted to the left or right. Then an approximately 200mm long indicator arm swung sideways out of the body, indicating the direction of travel. These direction indicators, which may seem bizarre from today’s perspective, were soon replaced by amber/yellow flashing lights, activated by turning the ring via a central control unit.

Side note – Ever wondered where the clicking sound made by indicators comes from? The circuit used by early vehicles to send current to the lights involved a bi-metallic spring which would heat up as soon as you activated the turn signal.

Since the two metals comprising the spring had different thermal coefficients, the metal strip would want to bend and contort from its original shape. As it did this, the bimetallic spring eventually made contact with another terminal, completing a circuit, and sending current to the turn signal lights. That bi-metallic spring bending as it heats up and cools down to touch the two different contacts created the clicking noise.

However, cars nowadays, with on-board computers sending the required signals, mostly simulate the clicking sound through speakers, usually depending on a relay under the dash.

The 1950s: the debut of the column gearshift and power steering

In the 1950s, the steering wheel became even more of a central interface between car and driver – as a control centre for new comfort functions and greater safety. In 1951, Mercedes-Benz introduced a gearshift on the steering column in the 300 'Adenauer-Mercedes' (W 186) and in the 220 (W 187), which led to an improvement in comfort for driver and front passenger. This was because at that time, the front seats usually consisted of a continuous bench which could accommodate up to two co-drivers.

Until the 1970s, the gearshift lever on the steering column remained a widespread method of operating the transmission. At Mercedes-Benz, it returned in 2005 with the Direct Select automatic selector lever, which freed up the centre console for other purposes. Another steering wheel function was added in 1955 with a lever for the headlamp flasher. The steering itself, however, was often exhausting to operate, despite the large steering ratio and the protruding steering wheel diameter. For this reason, Mercedes-Benz introduced power steering in 1958 in the 300 saloon.

The 1960s: reduced risk of injury thanks to safety steering wheel

In 1959, Mercedes-Benz revolutionised automotive engineering, particularly in terms of accident protection, with the 'Fintail' (W 111). This saloon was the world’s first vehicle to feature an integrated safety concept consisting of a stable passenger cell, crumple zones, a new safety steering wheel with a large, deformable (thus impact-absorbing) baffle plate which reduced the risk of injury in the event of a collision, and a split steering column which was offset to the rear. This made it possible to avoid the so-called lance effect. In earlier vehicles with a rigid steering column, serious injuries resulted from the steering column being pushed towards the driver in a frontal impact. To further increase safety, Mercedes-Benz introduced a patented safety steering system with a telescopic steering column and impact absorber, which became standard on the entire passenger car range in 1967.

In addition, the first combined lever made its debut in 1959 in the 'Fintail' and 'Ponton.' Following the motto “two for one,” it integrated the indicator and headlight flasher functions. In 1963, the lever was extended, and the windscreen wipers and windscreen washer system functions were also added. This was another pioneering feature in Mercedes-Benz cars, as the windscreen wipers in contemporary cars were activated with a pull switch on top of the instrument panel.

The 1970s and 1980s: all about safety

The four-spoke safety steering wheel introduced with the 350 SL Roadster in 1971, providing even better impact protection thanks to a wide padded plate with an impact absorber. The spokes doubled up as supports for the rim, absorbing the forces in the event of a collision, and transmitting them in such that the steering wheel rim would not break. The horn ring had already had its day, and the buttons for the horn were moved back to the centre of the steering wheel.

1975: The first cruise control

In December 1975, the Mercedes-Benz 450 SEL 6.9 was one of the first automobiles to be equipped with a cruise control system as standard. The world’s first radar-supported Distronic proximity control system, which maintains a constant distance to the vehicle in front, had its world premiere in 1998, also in the S-Class (220 series).

1981: The first airbag

Another decisive change in the steering wheel design came in 1981 with the introduction of the first driver airbag in the S-Class (126 series). Hidden behind the protruding baffle plate was a new restraint system, which offered a safety standard never before achieved in the event of a collision. However, early airbags were voluminous, so the baffle plate had to be quite large. But as the tech developed, it became possible to fold the vacuum-packed airbag into ever smaller sizes, allowing for a more aesthetically pleasing design solution.

In 1992, the driver airbag became standard equipment on all Mercedes-Benz passenger car models. The passenger airbag followed in 1994. The airbag inflates to a diameter of 720mm and a volume of 64 litres within 30 milliseconds on impact.

“Today we have the most compact airbag on the market,” says Marcus Fiege, head, steering wheel development, Mercedes-Benz.

1998: The first multifunction steering wheel

Another technical revolution was added in 1998 in the form of the multifunction steering wheel, and the debut of the COMAND (Cockpit Management and Data) system in the S-Class model series. It was not only the multitude of vehicle functions, but also the advance of new devices for information, navigation and entertainment that required a rethink of the vehicle operation and its display concept.

With a new, standard multifunction steering wheel, the driver had all the important information, like the car radio, car phone and a display in the middle of the instrument cluster with up to eight main menus, available at the touch of a thumb.

2005: The reintroduction of the steering wheel gearshift

2005 saw the debut of the then new models of the M-Class and S-Class with redesigned cockpits: the automatic selector lever moved from the centre console to the steering column. The new Direct Select gearshift, as originally intended, created space between the driver and front passenger and made operation even easier.

Additional steering wheel gearshift buttons enabled the manual pre-selection of the seven gears. From 2008, the SL Roadster was available with the 7G-Tronic sports transmission with steering wheel gearshift paddles.

From a polygonal to a geometric, round shape with flowing spokes

With the new functions, more and more cables, circuit boards and sensors found their way into the steering wheel. To accommodate them and the airbag, the steering wheels in the 2000s grew rather bulky.

In the course of time, however, the design became more and more refined. From the initial polygonal shapes, geometric forms with a circle in the middle and flowing spoke shapes developed.

2016: First touch-sensitive buttons in the E-Class

The 2016 E-Class was the first car in the world to feature touch-sensitive buttons on the steering wheel. They allowed the entire infotainment system to be controlled by finger swiping – without having to take your hands off the steering wheel. This allows the driver to control all the infotainment system's functions easily and intuitively, and just like your smartphone screen, pressing the touch control buttons triggers the function selected with swiping gestures. A further four buttons per switch panel took care of familiar functions, like volume control and telephone control.

2020: The capacitive steering wheel in the new E-Class

The new generation of steering wheels with capacitive hands-off detection will soon be launched in the E-Class, with a two-zone sensor mat located in the steering wheel rim.

The touch-sensitive buttons integrated into the steering wheel spokes now also function capacitively, reducing mechanical operating surfaces to a minimum. The seamless control panels, which are divided into several functional areas, are integrated flush with the spokes.

As with a smartphone, touches are recorded and evaluated via capacitive sensor technology, which enables intuitive operation via swiping gestures and pressing of familiar symbols. The high-quality materials have been selected in such a way that operation is possible even in an interior heated up by sunlight.

Perfect proportions

The Mercedes-Benz steering wheel is available in three versions: Sport, Luxury and Supersport.

“It is the most beautiful steering wheel we have ever built,” says Hans-Peter Wunderlich", adding, "the proportions of the airbag, spokes and rim are absolutely harmonious. The airbag is not concealed, but staged as a flattering sphere.”

In the “Luxury” version, the spokes form a chalice inspired by elegant Callas flowers in a black panel look, in which the central sphere floats.

In the “Supersport” version, it is held by two double-decker spokes in black panel design, reminiscent of the wheel wing nuts of sports cars. The steering wheels thus stage high-tech, combining cutting-edge tech with Mercedes' history of motorsport.

The size of the steering wheel has remained the same compared to the previous generation. Mercedes-Benz has developed fixed sizes for steering wheels. The steering wheel average is 370mm (Supersport) to 380mm (Luxury), depending on the version. The steering wheel rim is 29mm wide and 42 to 44mm deep.

“The steering wheel rim is the secret kingmaker of a steering wheel. Its geometric design is a science in itself that cannot be found in any textbook. The wreath must fit snugly in the hand. If it is a millimetre too much, it feels unpleasantly bulging. If it’s a millimetre too little, it feels like it’s starved. And that impression then clouds the overall feel of the car,” says Wunderlich.