INTERVIEW: Frank Knothe on 40 years developing the Mercedes SL

Frank Knothe

The new Mercedes-Benz SL has just been unveiled and recently we looked back at the R107 SL range celebrating its 50th anniversary. We chatted to one of the main engineers, Frank Knothe, who was integral to the development of the SL range for no less than four decades. 

Words: Wilhelm Lutjeharms
Pictures: Mercedes-Benz

Dipl.-Ing. Frank Knothe was one of the key men in the engineering and development of Mercedes-Benz SLs from 1966 to 2006. In his long-spanning career, he worked first on the W113 Pagoda when he joined the company, all the way up to the R230 (as well as the first-generation SLK (R170)), during a four-decade stint at the iconic Stuttgart-based marque. 

Mercedes SL Pagoda

What was your earliest highlight from your time working at Daimler?

One of my first jobs at Mercedes was installing the M130 engine (2.8-litre, six-cylinder) into the 280SL. This was my first recollection of the Pagoda. However, at that time development engineer Erich Waxenberger wanted more power for the car, so he installed the 6.3-litre, V8 engine in the Pagoda. It was a special occasion when he presented the car to the board of management. This Pagoda pulled away with spinning tyres and smoke, partly owing to the terrible weight distribution… the board decided it was not the right project!

What notable changes were focused on during the development of the R107?

Mercedes R107

With the R107 we developed a totally new suspension setup and axles – the latter similar to the W114/W115. There was also a huge push to increase passive safety. The strengthened A-pillars were important, especially for the American market for rollover protection. 

Why was the R107 in production for nearly two decades?

The R107 was in production from 1971 to 1989 for no single reason. It sold well, and unlike today, there were no legal or emissions-related reasons to release a new car. Obviously, we were working and developing its successor. My personal relationship with the R107 is special, as it was the first car and range that I was totally engaged with.

Frank Knothe

I actually bought a facelifted model in the late 80s, a 300SL. It was a car that formed part of our Mercedes-Benz fleet for a number of years as we were busy developing the R129. We used it to do comparisons with the new model. I also have an old Austin-Healey. 

The SLK was a totally new concept for Mercedes-Benz, much more compact than all its previous roadsters. How did this car come about?

Mercedes SLK R170

The discussions about this car started already in late-1980s. The Mazda MX-5 came to market and we were thinking of developing a competitor. We actually could have brought the SLK to market earlier if we finished our discussions earlier. In the end, it wasn’t such a bad idea to take our time in developing car, as we then launched the car with a retractable hardtop, a unique selling point of the car at the time.

In terms of electronics, the R230 clearly moved the SL to a new level?

Mercedes SL R230

The R230 was, for me, a very satisfying project. The dynamic capability of the car was high on the priority list. The result was that we installed the ABC (Active Body Control) suspension system. We were quite proud of the fact that we caused a little headache for our colleagues at Zuffenhausen (says Frank smiling). 

Of all these SL generations you helped to develop, is there a model that stands out for you?

Mercedes SL

I think all cars are highlights. My heart beats for all the models. But sometimes it is the people you meet, work with or the special memories you make that connect you on an emotional level with a car. That is not to say that the one car is better than another one.

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