The rear-engined revolution – why did it take so long?
Between 1934 and 1939, Mercedes-Benz and Auto Union dominated Grand Prix racing, Mercedes with front-engined cars and Auto Union with rear-engined designs by Dr Ferdinand Porsche. Both developed streamlined, low-drag bodywork and supercharged engines delivering more than 600bhp. While both won races, Mercedes was generally more successful.
Mercedes used a straight eight, De Dion rear suspension and independent front suspension via wishbones and coil springs. The car was conventional in layout – but very advanced and soundly engineered in detail.
Auto Union used a V16 with a fuel tank between the driver and engine and a five-speed transmission mounted behind the motor. A similar layout is universally used in F1 today. So far, so good… Front suspension was via trailing arms while swing axles were used at the rear. Those trailing arms gave a front roll centre at ground level, while the rear swing axles gave an extremely high rear roll centre, probably more than 380mm above ground level. When cornering, the high rear roll centre caused oversteer due to ‘jacking’ and high vertical loadings on the outside rear wheel. To compound the felony, the swing axles gave excessive camber change with bump and droop, causing large changes in rear grip over bumps and ripples. This resulted in severe, unpredictable oversteer – and the Auto Union’s reputation for evil, unpredictable handling. (Anyone who has driven a Triumph Herald or Renault Dauphine will understand…)
Despite the poor handling, Auto Union did win races thanks to its powerful engines, good straight-line traction – and the genius of drivers Tazio Nuvolari and Bernd Rosemeyer…
The Auto Union’s suspension problems were not well understood at the time. Its tricky handling was incorrectly attributed to the rear-mounted engine – causing a widespread and deep-rooted prejudice against such a layout.
As a result, front-engined designs would remain dominant until Cooper moved the goalposts in the late 1950s.
The rear-engined layout brings many benefits, including lower frontal area, lower centre of gravity and more rearward weight distribution. This gives lower drag, lighter overall weight (no propshaft) and better traction.
The car’s polar moment of inertia is lower, giving improved transient response. A less obvious benefit is the ability to provide a set-up that allows the driver to steer via the throttle.