Suspension and brakes – AUDI QUATTRO RALLY CAR MANUAL

Suspension and brakes

The suspension of the rally-specification Quattros was MacPherson all round, with heavily braced steel lower wishbones. Springs and dampers came from Boge – not a supplier with much rally pedigree but one which had a lucrative commercial agreement with Audi and was happy to plough some money and expertise in to the programme.

For rallies such as Corsica, the gauge of steel used, sizes of the tubes and amount of cross-bracing was pulled back to a minimum in order to help the Quattro to shed weight. For the Ivory Coast and Safari rallies in particular, the whole setup required considerable extra bracing and a granite-like feel to withstand flying over the African roads at full tilt.

At each end of the car, a steel subframe held everything in place and equally worked well for the ease of removal, repair and replacement of suspension parts at the roadside. The definitive design was in place for the 1981 Sanremo Rallye, allowing the team to switch from asphalt to gravel-specification setups in the space of five minutes.

With the arrival of significantly greater freedoms regarding materials in Group B, by mid-1982 Audi was already investigating alternatives for any benefit that they might bring. Aluminium, titanium and plastic were all built and trialled in the construction of chassis and suspension components. Almost exclusively, however, the suspension retained steel arms with aluminium fittings.

In 1985 the single Audi Sport quattro entered for Walter Rohrl in Corsica appeared to be much more like a racing car in its demeanour than on any previous asphalt event. This was a new chassis, one of two, built with input on the suspension mounting and geometry from Dieter Basche, the legendary BMW motor sport engineer, who managed to shave 12mm off the ride height while making the car suppler on the road surface.

Great things were expected of Rohrl and the new bespoke asphalt car – to the point that Ferdinand Piech was in attendance. That he went out early in the rally was the beginning of the end for Roland Gumpert’s tenure in charge of Audi Sport, although the retirement was due to a bad batch of brake discs, of which two sat broken on the front wheels of Rohrl’s car.

The brakes for the Quattro were an area that required massive and continual development. For one thing, they were being asked to slow 30-40% more mass than the brakes of a contemporary Ford Escort RS1800 had to deal with and also to rein it in from a significantly higher speed. Vented 280mm discs from AP were fitted at the front, with 245mm discs at the rear – the same setup and hardware as Porsche’s Le Mans-winning 935. There was no servo assistance but the balance could be changed from inside the car to adapt to changing conditions and wear.

The size of the brakes did not change considerably, even though the available power leapt up from one season to the next. This became a particular problem with the arrival of the 20-valve short wheelbase cars, which became fairly notorious for brake issues in a very short time. At the 1984 Sanremo Rallye, the Audi Sport quattros fielded for Rohrl and Blomqvist featured water injection cooling on the brakes for the first time.

For Rohrl’s magnificent final world championship victory in the Sport quattro S1, the 1985 Sanremo Rallye, the water cooling was upgraded to spray an additional fine mist of water directly on to the brakes to bring them down from the critical area of 700+ degrees back down to a reliable 500+ without causing breakages.

One aspect of the brakes that was never really sorted out was a functioning handbrake. In 1982-83 one of the strengths of two-wheel drive was the ability to whip around any hairpins or tight junctions with the help of the handbrake. Because the Quattro’s transmission was solid, it was simply impossible to lock the rear wheels only.

The only time in which the handbrake could potentially have been used was in the era of the final bewinged Sport quattro S1 in 1985-86, with the introduction of unlockable centre diffs. There is no evidence in the video footage of such a brake being used on a rally, but it is clear that for Rohrl’s assault on the 1987 Pikes Peak there was a fully operational handbrake in place.

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