NSU Rennmax
The dominator
When NSU decided to attack the 250cc class of the World Championships, they produced a machine so superior it utterly dominated for two years.
By the time the Allied bombing raids had ceased in late 1945, little remained of the once-proud NSU factory. For the previous six years, NSU had been forced to switch from its core business of producing motorcycles to production of aviation components, the unique Kettenkrad personnel carrier (basically a motorcycle fitted with chain-track), and military motorcycles. As such it was a prime target, and came in for constant bombardment. It was déjà vu for the company at Neckarsulm, near Stuttgart, which had suffered a similar fate during the 1914-18 war, and had barely survived the Great Depression.
So it was quite remarkable that only six years after the end of WW2, NSU was once again up to full steam. In fact, if the production of the Quickly moped was counted, NSU was the largest producer of motorcycles in the world. And as soon as possible, the company planned to pick up where it had left off with racing. Prior to 1939, NSU had an exotic 350cc double overhead camshaft supercharged parallel twin producing 68 bhp and capable of around 200 km/h. Naturally that project had lain idle until things began to return to some degree of normality, which saw Albert Roder ‚
become Chief Designer in 1947. One of his first tasks was to redesign the 350 to 500cc, and because Germany was barred from membership of the F.I.M. (which banned supercharging post-war), it remained supercharged for use in Germany only.
Roder’s next project was a four-cylinder 500, along the lines of the Gilera, which was raced locally in both solo and sidecar form in 1951. The plan was to use the 500-4, designated R54 in international competition when Germany was readmitted to the FIM, but NSU management saw the company’s future in the production of lightweight machines, and decreed that any factory-supported racing would concentrate on the smaller classes. Thus it was that a new racing 125, the R11 Rennfox, came to light in mid-year 1951. The svelte machine employed the same dimensions of 54mm x 54mm bore and stroke as the R54 as was basically one cylinder of the 500, producing 12 bhp at 10,500 rpm.
Like the NSU road machines, the R11 engine was housed in a pressed steel frame, with leading link front forks and a single rear shock absorber. By 1952 power had risen to 14 bhp at 11,000 rpm, but Roder was secretly at work on what would be his masterpiece – a DOHC parallel twin racer which became the R22 Rennmax, also with 54 x 54 engine dimensions. Initially the 250 put out 25 bhp, but before the 1952 season was out, the Rennmax was pumping out 29 bhp at 9,000 rpm, driving through a 4-speed gearbox. The twin overhead camshafts were driven by shafts and bevels in a pair of tunnels in a V-shape on the right side of the engine. One break in tradition was the use of torsion bars instead of valve springs, but these were soon replaced by conventional hairpin springs. A pair of six volt batteries sat under the seat and fired twin coils, and the engine breathed through a pair of 24mm German-made Amal Remote Needle carburettors. Unlike the Rennfox, the Rennmax used a tubular steel cradle frame, with rather spindly telescopic front forks and twin rear shock absorbers on the swinging arm. All-up weight was 148kg.
NSU entered a Rennmax for Wilhelm Hofmann at the 1952 German Grand Prix at Solitude, but when the German was injured in practice, British rider Bill Lomas took over the seat. In a ferociously-fought race, Lomas forced his way to the front, only to have the engine snap a conrod on the final lap.
With the supremely talented Werner Haas in the saddle, the Rennmax was back for the final race of the season, the Grand Prix of Nations at Monza, Italy. It was expected to provide little opposition to the allconquering Moto Guzzi squad, but came within millimetres of a fairy tale victory when Haas and World Champion Guzzi teamster Enrico Lorenzetti virtually deadheated. Both riders were given the same race time – 50 minutes 7.2 seconds, but officials declared the Italian the winner. Amid howls of protest from German supporters, the Italian Federation quickly released an official photograph that showed the Guzzi had indeed won the race, albeit by a wheel. There was little doubt however, that the NSU was now the fastest 250 on the grid.
The result galvanised NSU into an all-out effort for the 1953 250cc Championship, with a four-rider works team comprising Haas, Otto Daiker, Hubert Luttenberger, and Briton Bill Lomas. One of Lomas’ duties was to teach Haas the intricacies of the Isle of Man TT circuit, which he did rather effectively! The factory sent a pair of production NSU Max road bikes to the Island more than two months ahead of the races, and Lomas and Haas completed countless laps in the lead-up to the race.
The 1953 Rennmax was all-new and now housed in a pressed steel frame with a bolted-on tubular steel rear section to which the shock absorbers were attached. With the 1952 tubular frame version, riders had complained of vibration, which was basically eliminated with the stiffer pressed steel frame, at the expense of extra weight totalling 166kg. The factory also saw the new frame as a closer reflection to what was being offered on their road bikes. The flimsy telescopic forks were gone, replaced by leading link forks with pressed-steel blades. ‚
Engine power was now up to 32 bhp at 10,000 rpm, compression ratio had risen to 9.8:1 and carburettors were now 25.4mm bore. The new 250 won first time at Floreffe, Belgium in Lomas’ hands, then Haas took a 125/250 double at the international meeting at Hockenheim. Then came the TT – the opening round of the 1953 World Championship.
Despite their extensive reconnaissance, both
Haas and Lomas crashed in official practice, and although Hass was able to race, Lomas was out for an extended period and never raced for NSU again. A last-minute effort was launched to draft World Champion and lead Gilera rider Geoff Duke into the NSU team to ride Lomas’ 250, and Duke went as far as testing the machine at Jurby Airfield on the Isle of Man before the ACU of GB vetoed the plan on the grounds that he had not practiced on the motorcycle he intended to race. Haas finished second to the vastly experience Guzzi team leader Fergus Anderson – an excellent achievement on the world’s toughest circuit. But better was to come. Two weeks later, he won the Dutch TT at Assen, followed by the West German GP at Schotten. Second place at the Ulster GP behind team mate Reg Armstrong and another runner-up to Lorenzetti at Monza gave the 26-year old German the 250cc World Championship to add to the 125cc title he had already clinched. Drafted into the 250 squad in place of the injured Lomas, Irishman Reg Armstrong turned in a series of impressive rides to end up a fine second to give NSU a 1-2 in the 250 standings.
For 1954, the works Rennmax received a number of significant changes, including the use of angular aluminium streamlining which featured a pronounced ‘beak’ over the front wheel. Camshaft drive was
changed from twin shafts on the right to a single shaft on the left, driving the inlet camshaft. Valve sizes were increased and the traditional ‘square’ bore and stroke gave way to an over-square 55.9mm x 50.8mm. A five-speed gearbox replaced the fourspeeder. To the dismay of the opposition, maximum power was up to 39 bhp at 11,500 rpm. With the slippery fairing fitted, top speed was reputed to be around 217 km/h (135 mph).
The 1954 World Championship was a walkover for NSU; Hass winning the first five races to easily claim the 250cc title, with Rupert Hollaus becoming Austria’s first World Champion in the 125cc category, winning four of the six rounds. Indeed, the 250 NSUs won every race in which they started; 24 out of 24. Late in the year, a 288cc version appeared in a German Championship round ridden by Hermann Müller, winning easily against classy opposition with a race time only fractionally slower than the 500cc race winner. There was however a sombre end to the season when the new 125cc World Champion Hollaus crashed fatally in practice for the final GP at Monza and the NSU team withdrew from the meeting.
Then came the bombshell. NSU announced in October 1954 that it would no longer contest the World Championships with a works team, but it would produce a ‘customer’ 250 based on the road going Max single, called the Sportmax. Prototypes of this machine had been in existence for two years and, with development, had proven to be very competitive. The Sportmax would go on to provide privateers with reliable and fast equipment in the 250 class for many years to come. The exotic works Rennfox and Rennmax however, were never raced again. With the closure of the NSU works team,
Werner Hass retired from racing, but was killed on 13th November, 1956 when the private aircraft he was piloting crashed shortly after take-off at Neuburg/Danube aerodrome in Germany.
Fast forward
Wolfgang Schneider is the acknowledged expert on the Rennmax racers. Here he tells the tale of the fate of these landmark motorcycles post-1954. Fortunately several are preserved in the AUDI Tradition museum at Ingolstadt, Germany.
“Three Rennmax were built in 1952. None survived. They were scrapped right after the end of the season, including two tube frames based on the Norton Featherbed. One of the engines is preserved, another incomplete in parts, all in the AUDI Tradition inventory. In 1953 six were built, three of which have a tradition at AUDI, one at the Neckarsulm two-wheeler museum and two in a California ‚
collection, one of which was converted into a tubular frame for the Scuderia Geoff Duke in 1957, the collector also had the sheet metal chassis for this machine.
“In the 1954 there were again six machines, however after the first races in Floreffe and Hockenheim these first four were completely disassembled and new, stronger frames were manufactured, as well as six new crankcases with three-point engine mounting, which instead of Electron were cast with heavier but more stable Silumin aluminium alloy. Parts of these first frames were given to private drivers who wanted to build a Sportmax themselves.
“The 1954 season almost never started because NSU already had problems with a shortage of skilled workers on the one hand and high costs due to automation with feared sales problems of individual products (except scooters and mopeds). Immediately after the 1954 season, a temporary stop of at least two years was decided by the board. All other bright minds went about constructing Wankel and Prinz cars. All racing engines were stored for confidentiality reasons. Only four exhibition machines with empty magnesium motor housings (the hapless first series) were assembled with unprocessed cylinder heads and too small carburettors to be exhibited abroad and at trade fairs or with large importers.
“These ingenious engines were locked up in the factory until they were taken over by VW in 1969. Wilhelm Herz then disposed of them to a scrap metal dealer. VW had ordered that they be destroyed, which fortunately did not happen. Only one, the 288cc raced by H.P. Müller, was brought by VW to Wolfsburg because it was obviously the most beautifully painted. It also had an empty magnesium dummy engine, very annoying when in 1997 AUDI Tradition wanted me to rebuild it. The motor was just a shell without any value, because the magnesium housing was also completely broken on the inside, so that nobody was able to secretly spy on the factory secrets of these unbeatable engines at a motorcycle fair at night. Even engine parts from the 1953 version went illegally to Italian manufacturers, who had probably set up specialists to get at them under all circumstances.”
Originally, NSU set out to put German engineering to the forefront of Grand Prix racing, at a time when it was the domain of the Italian factories. Ironically, NSU’s total dominance of the Lightweight classes was one reason for their decision to pull out after the 1954 season, but there are other reasons, as Wolfgang explains:
“With racing machines that no one can buy, you would ‘break’ motorsport with long-term victories. In addition to economic reasons, this was one of the main reasons why NSU retired from factory racing at the end of 1954. I have read the minutes of the board meeting. FIM was also to blame for the fact that Italian plants withdrew. In the winter of 1953/54 there were plans to no longer allow works drivers to be awarded the World Championships. The millions of euros spent on factory racing machines were no longer justified, especially since all manufacturers had started to experience declining sales as a result of the economic boom and to switch away from motorcycles to small cars. In the late 1950s to the early 1960s, motorcycle sales had almost completely stopped. Only mopeds, bicycles and scooters were in demand in Germany.”
“These ingenious engines were locked up in the factory until they were taken over by VW in 1969. Wilhelm Herz then disposed of them to a scrap metal dealer.”