Of the many rally victories recorded by Audi in the 1980s, the last one was particularly memorable: 20 years ago, on 11 July 1987, Walter Röhrl and his Audi Sport quattro S1 won the Pikes Peak Hill Climb in the US state of Colorado.

Following Audi’s withdrawal from the World Rally Championship in the previous year, this success marked the seamless transition of "Vorsprung durch Technik" into series production. After the company retired from rallying, quattro technology continued its success story on the road – Audi has sold 2.5 million cars with permanent four-wheel drive up to the present day.

Walter Röhrl and Audi, the best driver and the most successful rallying team at that time, enjoyed a close and always extremely intensive relationship. Röhrl, the world champion of 1980 and 1982, had joined the Ingolstadt team in 1984 at a time when the brand with the four rings dominated the entire rallying scene.

The permanent four-wheel drive system left the rear-wheel-drive competitor vehicles with no chance whatsoever. A mere two years after first testing the Audi quattro at the end of 1980, Audi had already clinched the manufacturers’ world title. The Finn Hannu Mikkola won the drivers’ world championship in 1983, and in the following year Audi took both titles, with Stig Blomqvist from Sweden topping the drivers’ rankings.

From 1984 Audi’s rivals – Peugeot, Lancia, MG and Ford – also featured four-wheel drive to compete against the brand’s new racing car, the Sport quattro, whose wheelbase had been reduced to 222 centimetres. The regulations of what was then Group B imposed few restrictions in terms of technology; the fierce competition resulted in engines which generated over 370 kW (around 500 bhp). The supercar era ended in 1986; Audi withdrew from the World Championship.

In order to acquaint the US public, too, with the "art of engineering" (the slogan in the USA), Audi had entered the world’s best-known hill-climb race for the first time in 1984 – the "Race to the Clouds" on Pikes Peak in Colorado.

4,301 metres high, it is in the Rocky Mountains and is named after the explorer Zebulon Montgomery Pike, who charted it by order of the US army. The first race was staged in 1916, and subsequently took place on a regular basis, generally on the national holiday, 4 July. At the start of the 1980s the organisers introduced a category for rallying cars – an ideal stage for high-tech brands such as Audi.

The Pikes Peak track is unique. The International Hill Climb, as the race is officially known, takes place in an environment where mountain racers feel at home. It starts at a height of 2,866 metres at Crystal Creek, and the route to the summit is 19.99 kilometres in length with an average upward gradient of seven percent.

The winding track, which has 156 corners and leads through areas of bare rock, largely consists of reddish sand and gravel under which is a solid clay surface. The track is six metres wide on the straights and up to 15 metres wide in the corners; there are no guardrails. In the upper section, the track winds its way along sharp ridges like the edge of a table; at the "Bottomless Pit" there is an abyss 1,800 metres deep.

Just as in the World Rally Championship, Audi also enjoyed great successes right from the start on Pikes Peak. In 1984 Michèle Mouton from France came second in the Audi Sport quattro, despite being slowed down by a minor defect; in the following year she won the race. In 1986, the American motor-racing legend Bobby Unser set a new record in his Sport quattro S1 with a time of 11:09:22 minutes.

The S1, with which Röhrl took part as the only Audi driver in 1987, was a high-tech driving machine of pure, maximised functionality. The 2.1-litre five-cylinder engine, installed longitudinally at the front of the vehicle, had a nominal power output of some 440 kW (around 600 bhp) at 8,000 rpm and 590 Nm of torque at 5,500 rpm. At the top of Pikes Peak the power output actually available would have been approximately 330 kW (around 450 bhp).

A circulating-air system continuously maintained boost pressure in the large KKK K28 turbocharger, crucially improving the turbocharger’s response in the thin mountain air. When the throttle was closed, the charge air shot into the exhaust, where it was reheated with the exhaust gas, keeping the turbine revs up.

The power of the five-cylinder engine was transmitted via a six-speed gearbox, which even then used the dual-clutch principle – a pioneering feat by Audi – on a quattro driveline equipped with three locking differentials. The four 16-inch wheels, fitted with Michelin tyres, were mounted on double wishbones. On Pikes Peak, where the route almost always led upwards, Audi used a small and correspondingly light brake system.

Weight-optimised in all areas and converted into a one-seater, the Audi Sport quattro S1 weighed a mere 1,000 kilograms or so on its appearance in Colorado. The outer skin consisted of sheet steel and plastics, and was built on a tubular space frame. Powerful wings at the front and rear, developed in the wind tunnel, kept the angular body pressed down towards the ground; there were even wide air deflectors on the sides of the car.

Walter Röhrl, the reserved perfectionist, was a virtually unknown European as far as American racing fans were concerned, and was taking part at Pikes Peak for the first time. But the dominance with which he took control of proceedings from the outset was evidence of his exceptional talent.

Despite extensive preparations, the Peugeot team, with Jean Todt at the helm, only made an impression in qualifying: when there was an electronic fault in the circulating-air system of Röhrl’s car, Ari Vatanen (Finland), the strongest of the three Peugeot drivers, took advantage to record the best time in his 205 T16.

On 11 July 1987, the day of the race, the organisers made the drivers start the race in the reverse order of their results in qualifying. Vatanen brought up the rear of the field, with Röhrl one place in front of him. The man from Regensburg, always calm and collected at the wheel, conquered the world’s most elevated highway in a new world record time of 10:47:85 minutes.

He reached sixth gear in the S1 on four occasions, and at the quickest point of the track was measured at a speed of 196 km/h. Röhrl took each of the 156 corners with razor-sharp precision and performed full power-slides around the hairpin bends; sometimes the edge of the car was actually hanging over the precipice.

Ari Vatanen lost the duel, completing the course in 10:54:38 minutes, almost seven seconds slower than Röhrl. Peugeot cited a broken hose clamp and resulting boost pressure problems. Only in the following year – Audi having withdrawn from the Pikes Peak race after achieving a hat-trick of victories – did Vatanen succeed in winning, this time at the wheel of a Peugeot 405.

Walter Röhrl was emotional and happy following his victory, and seemed close to tears. He later stated: "All I can say is that it was great to take part. It was crazy, but often it is in fact the crazy things which are the best in life. It was the very pinnacle of what can be done with a rally car."

Röhrl and Audi continued to work together for several more years, with the double world champion taking on an advisory role, helping the brand to continue quattro technology’s outstanding success on the road. Starting from as early as 1982, Audi had incorporated five more four-wheel-drive models into its range in addition to the legendary Ur-quattro of 1980.

In 1988 followed the Audi V8, with quattro drive as standard, which broke new ground with its V8 engine generating 185 kW (250 bhp). In its racing-car form it won the German Touring Car Masters – yet further proof of the quattro principle’s supremacy in motorsport.

From 1990 onwards the S models, all of which were also fitted with quattro drive, played their part in further enhancing the brand’s image of cultivated sportiness. Audi then introduced a model series with even more pronounced levels of dynamism – the RS line. And since 1995 the powerful TDI diesel models are also available with quattro drive – another harmonious combination.

In 1999 the four-wheel-drive principle made its way into the compact class. The power produced by the transversely installed engine was distributed by an electronically controlled Haldex transmission unit in the Audi A3, Audi TT and Audi TT Roadster. And then in 2003 the TT featured the innovative DSG dual-clutch gearbox with what was in principle the same technology which had paved the way for Walter Röhrl to conquer Pikes Peak.

A further innovation made its debut in 2005 on the Audi RS 4. The new generation of mechanical Torsen differentials features asymmetric/dynamic torque distribution; the flow of power in the ratio 40:60 between the front and rear wheels allows for even sportier driving.

There are two figures which illustrate the outstanding success of quattro technology particularly well: Audi, the worldwide market leader for premium-class passenger cars with four-wheel drive, currently has no less than 84 four-wheel-drive variants in its model range. And from 1980 to today, the brand has produced 2.5 million cars with quattro drive.

- Josef Schloßmacher - photo AUDI