The 1937 Mercedes-Benz W125 remains an icon in motorsport history, representing the pinnacle of pre-war Grand Prix racing car design and performance. Developed by Mercedes-Benz for the 1937 season, this formidable machine was not just fast; it was utterly dominant. Achieving a staggering speed of 193 mph on the legendary Spa circuit, the Mercedes W125 swept through the season, securing victory after victory and etching its name into racing folklore. The results of the 1937 season are a testament to its overwhelming superiority, with wins across prestigious Grand Prix events in Tripoli, the Avus Race, Germany, Italy, Brinn, Monaco, and Switzerland.
The mercedes w125 was conceived as the successor to the already successful Mercedes-Benz W25. It also marked the final Mercedes-Benz contender built under the 750 kg formula regulations, an era defined by unbridled power and speed. The racing regulations of the period, spanning 1934 to 1937, were remarkably permissive concerning engine size and aspiration. This lack of restriction paved the way for the creation of incredibly powerful and rapid racing cars. In 1937, the primary constraint was a maximum weight limit, increased to 850 kg from the previous 750 kg of the 1936 season. This environment of regulated freedom allowed engineers to push the boundaries of automotive technology, resulting in machines like the mercedes w125.
At the heart of the mercedes w125 lay an exceptionally robust foundation: a tubular oval frame constructed from specialized steel, reinforced with four cross members. This chassis design benefited from insights gained from production car development, drawing parallels with the frame used in the 1938 Mercedes-Benz 230. The suspension system was a leap forward in racing car technology. The front end featured double wishbones and coil springs, a configuration borrowed from the luxurious Mercedes-Benz 500 K and 540 K models, ensuring superior handling and stability. At the rear, a sophisticated double-joint De Dion axle maintained constant wheel camber, complemented by longitudinally mounted torsion bar springs and lever-type shock absorbers. Lateral links efficiently managed thrust and braking forces, transferring them effectively to the chassis.
Rudolf Uhlenhaut, a brilliant Mercedes-Benz engineer, played a pivotal role in refining the W125’s handling. Following extensive testing at the challenging Nürburgring circuit, Uhlenhaut revolutionized suspension design for Grand Prix cars. He inverted the conventional approach of stiff springs and minimal damping, opting instead for soft springs with extended travel paired with stiff dampers. This innovative setup, implemented in the mercedes w125, became a blueprint for modern Mercedes-Benz sports cars, prioritizing controlled compliance over jarring rigidity. Visually, the W125 retained a resemblance to its predecessor but was distinguishable by its three prominent cooling air inlets. For the high-speed Avus race on May 30, 1937, where Hermann Lang achieved an astounding average speed of 261.7 km/h, a streamlined body was fitted to further minimize drag. The transmission and differential were integrated into a single, compact unit. Powering the mercedes w125 was an advanced eight-cylinder in-line engine, the culmination of years of development of the Grand Prix engine program that began in 1934. Notably, the supercharger was strategically positioned behind the carburetors, marking a first for Mercedes-Benz racing engines by feeding the supercharger with the fuel-air mixture.
Although the mercedes w125 enjoyed only a single year of frontline racing, its adaptability was remarkable. Engineers could fine-tune the car to suit diverse racetracks through a range of adjustments, including different transmissions, fuel tank capacities, fuel mixtures, carburetors, superchargers, wheel and tire sizes, tire treads, and even subtle alterations to the car’s external dimensions. These modifications directly impacted engine power, torque, top speed, and gear-specific performance. A wide selection of eight different transmission ratios was available, along with two rear wheel sizes (7.00-19 and 7.00-22). For the Gran Premio d’Italia in Livorno on September 12, 1937, the factory reported an output of 592 horsepower (435 kW) at 5800 rpm. By this time, the engine displacement had grown to 5660 cc. This potent engine consumed fuel at an astonishing rate of one liter per kilometer, running on an aggressive blend of 88 percent methanol, 8.8 percent acetone, and trace amounts of other performance-enhancing substances. In race-ready trim for this configuration, the mercedes w125 weighed 1097 kilograms (1021 kilograms without the driver), which included 240 liters of fuel, seven liters of water, nine liters of engine oil, and 3.5 liters of transmission oil. On the test bench, engineers in Untertürkheim extracted up to 646 horsepower (475 kW) from the 222-kilogram engine. These figures translated to an exceptional power-to-displacement ratio of 114 hp (84 kW) per liter and an equally impressive power-to-weight ratio of 1.16 kilograms per horsepower. These performance metrics were groundbreaking for their time and remained unmatched for decades, as did Hermann Lang’s average speed record of 261.7 km/h from the Avus race.
Mercedes W125 Victories:
- Jul 25, 1937: German GP-Nürburgring (Rudolf Caracciola)
- Aug 8, 1937: Monaco GP-Monte Carlo (M. v. Brauchitsch)
- Aug 22, 1937: Swiss GP-Bremgarten (Rudolf Caracciola)
- Sep 12, 1937: Italian GP-Livorno (Rudolf Caracciola)
- Sep 26, 1937: Masaryk GP-Brno (Rudolf Caracciola)
Mercedes-Benz W125 Specifications & Performance:
| Feature | Specification |
|---|---|
| Engine | M 125 F V8 |
| Position | Front Longitudinal |
| Aspiration | Supercharged |
| Valvetrain | DOHC 4 Valves / Cyl |
| Displacement | 5660 cc / 345.4 in³ |
| Bore | 94 mm / 3.7 in |
| Stroke | 102 mm / 4.02 in |
| Power | 441.5 kw / 592 bhp @ 5800 rpm |
| Specific Output | 104.59 bhp per litre |
| BHP/Weight | 710.68 bhp per tonne |
| Redline | 6000 rpm |
| Body / Frame | Aluminum over Oval Tube Frame |
| Driven Wheels | RWD |
| Front Tires | 5.25×17 |
| Rear Tires | 7.00×19 |
| Front Brakes | Lockheed Hydraulic Drums |
| Rear Brakes | Lockheed Hydraulic Drums |
| Steering | Worm & Nut |
| Front Suspension | Unequal Wishbones w/Coil Springs, Hydraulic Shock Absorbers |
| Rear Suspension | De Dion Axle w/Torsion Bar Springs, Hydraulic Shock Absorbers |
| Curb Weight | 833 kg / 1836 lbs |
| Wheelbase | 2798 mm / 110.2 in |
| Front Track | 1473 mm / 58.0 in |
| Rear Track | 1412 mm / 55.6 in |
| Length | 4200 mm / 165.4 in |
| Width | 1750 mm / 68.9 in |
| Height | 1200 mm / 47.2 in |
| Transmission | 4-Speed Manual |
| Gear Ratios | 2.13:1, 1.37:1, 1.18:1, 0.94:1 |
| Final Drive | 3.52:1 |
| Top Speed | ~321.9 kph / 200.0 mph |
In conclusion, the mercedes w125 was more than just a racing car; it was a technological marvel that defined an era of Grand Prix racing. Its dominance in the 1937 season solidified its place in history as one of the most powerful and successful racing cars ever built. The legacy of the mercedes w125 continues to inspire awe among motorsport enthusiasts and engineers alike, representing a high watermark in automotive engineering and racing prowess.
