A car is a highly complex product. Before it can be launched, it has to be subjected to intensive testing.
This involves every vehicle’s qualities and technical components undergoing a thorough inspection, and every part being pushed to maximum load in order to see how the vehicle behaves under critical handling conditions. The results serve to determine what has been achieved – and ascertain the basis on which the car can be developed to production standard.
A car should demonstrate its various qualities above all while being driven. For this reason, chassis testing and tuning is a core element of much of the testing. This takes place both on company premises and on public roads. After all, it is on this terrain that the cars will eventually spend the vast majority of their service lives. An ideal test lap is one with a wide-ranging circuit profile that permits testers to gain a complete picture of the vehicle over a relatively short distance.
The tester’s ideal was discovered during the 1960s at the small town of Friedrichsruhe, around 30 kilometres from Heilbronn and 75 kilometres from Stuttgart. As mapped out by the Mercedes-Benz engineers, the test circuit measured exactly 34.5 kilometres in length and offered a range of opportunities to fully test and tune a car’s chassis. Two auxiliary shorter circuits measuring 18.9 and 26.5 kilometres respectively provided further possibilities for precise testing without the need to drive the longer lap. For test drives generate a mass of results and data – and the engineers’ improvement suggestions are provisionally implemented immediately after the test in order to gauge the effectiveness of the measures. This may mean, for example, that a different spring/damper combination is tried in order to improve handling characteristics. A detailed knowledge of the circuit is essential for precise evaluation of the results, which helps explain why the same routes are maintained year after year. Since test engineers know every inch of the track, they also know the precise spots that are likely to supply the right information for a particular issue. This is also handy for purposes of comparison, as one part of the job involves driving and testing the cars; the other is about being able to recognise exact improvement potential and suggest appropriate measures to achieve them. Only then can automotive development really take place.
The ideal test circuit for chassis testing offers a variety of surfaces, including asphalt, surface ripples, left-side and right-side unevenness, individual potholes, tight and long corners, as well as long straights for high-speed driving. Every possible set of circumstances is required to force the car react and in so doing generate information about the actual chassis set-up. At Friedrichsruhe – where such important model series as the S-Class (W 116 and W 126 series) and the SL-Class (R/C 107 and R 129 series) underwent chassis tuning – this is achieved over a circuit measuring just under 35 kilometres.
Since conditions were so perfect at Friedrichsruhe, the brand also chose the test circuit just an hour’s drive from Stuttgart as the venue for press driving events, when new cars were unveiled to journalists. Past events have included, for example, the presentation of the coupé from the 126 series, the Mercedes-Benz 500 E (W 124) and the convertible from the 124 series.
Friedrichsruhe has seen many changes over the years, of course. The motorway section embedded in the Friedrichsruhe circuit now has a speed restriction, for example, making it impossible to conduct the important “vmax test” – in other words, to push the vehicle to its upper speed limit. Such tests are not simply speed for speed’s sake; they are about ascertaining whether or not a car meets requirements in terms of directional stability and wind noise even at high speed. On other sections of the track, surface unevenness has been removed, necessary above all in order to determine ride comfort and road roar and tyre vibration characteristics (suspension, damping). There has also been an increase in the volume of traffic. On account of these changes, and for reasons such as the fact that better and more stable weather conditions were to be found in more southerly climes, Mercedes-Benz gradually reduced and ultimately abandoned chassis testing and vehicle tuning at the Friedrichsruhe test circuit in the mid 1980s.
But the Friedrichsruhe test circuit still has much to offer even today. Fundamentally it is just as it always was, and numerous parts of the circuit still allow conclusions to be drawn about a car’s chassis or general handling characteristics. Taking a drive around the circuit is an experience that is sure to repay dividends – perhaps even in one of the many Mercedes-Benz classics whose chassis were once tuned at Friedrichsruhe or in a model that underwent its original press presentation here.
The route of the test circuit could you download as PDF-File here.
Source: Daimler AG