Mercedes-Benz
W 125 Grand Prix car

Why it matters

The W 125 was Mercedes-Benz's Grand Prix car for 1937, the last season of the 750 kg formula, and one of the most powerful racing cars of the pre-war era. Its supercharged 5.66-litre straight-eight produced close to 600 bhp, and only nine were built.

How rare is it?

Six separate kinds of rarity – never combined into one number.

Each kind of rarity is rated separately and never combined.

Production

Every figure says what it counts.

Independent counts (e.g. engine and colour) are never combined into a calculated figure. Surviving examples are never presented as original production.

History

Developed for 1937 under Rudolf Uhlenhaut as the successor to the W 25K, the W 125 used a front-mounted M 125 F straight-eight with Roots-type supercharging and a four-speed gearbox. That season it won the Tripoli, German, Monaco, Swiss, Italian and Czechoslovak Grands Prix with Lang, Caracciola and von Brauchitsch. It was followed by the 3-litre W 154 when the formula changed for 1938.

Technical specifications

Engine

Transmission & drivetrain

Chassis, body & dimensions

Performance

“Not yet verified” means no source has been checked for that value yet. Nothing is estimated to fill a gap.

Identification guide

How to tell an original from a replica or later conversion.

The W 125 differs from its W 25 predecessor in a ladder-type frame of oval longitudinal tubes with round-tube cross braces instead of a pressed-steel frame, a de Dion rear axle on torsion bars, and a front axle with unequal-length double trapezoidal links and vertical coil springs. The wheelbase is 2798 mm, 293 mm longer than the W 25, and the drum brakes are 400 mm in diameter with 72 mm shoes. The M 125 engine has a 94 mm bore, 5663 cc displacement and float carburettors ahead of the Roots blower; crankshafts with five and with nine main bearings were both used. Two cars were fitted with fully streamlined bodies and 22/24-inch wheels for the 1937 AVUS race, which is a separate configuration from the standard Grand Prix car.

Sources

Each number links to the exact facts it supports.

1. 1
   Mercedes-Benz Grand-Prix racing car W 125, 1937 (Classic M@RS) Level A Mercedes-Benz Group AG (Classic M@RS, Mercedes-Benz Public Archive)

   • A total of eleven W 125s were built in Untertürkheim
   • eight-cylinder inline engine with Roots blower
   • float carburettors positioned upstream of the Roots blower
   • ladder-type frame made of oval longitudinal tubes with transverse bracing
   • dual trapezoidal control arms of unequal length ... vertically positioned coil springs
   • de Dion rear-axle ... torsion bars with hydraulic dual-piston lever-type shock absorbers
   • drum diameter remained at 400 mm ... brake shoes measuring 72 mm
   • extension of the wheelbase by 293 mm to 2798 mm

   Accessed 2026-11-12
2. 2
   1937 Mercedes-Benz W125 Specifications - Ultimatecarpage.com Level C

   • 9 cars built

   Accessed 2026-11-11
3. 3
   Mercedes-Benz W125 Level C Wouter Melissen · Ultimatecarpage.com · 2007-10-03

   • M 125 F Straight 8
   • Front, longitudinally mounted; M 125 F Straight 8
   • 5,660 cc
   • Bore / stroke 94.0 mm / 102.0 mm
   • Compression 8.8:1
   • Roots-type supercharger, two suction carburettors
   • 592 bhp / 442 kW at 5,800 rpm
   • at 5,800 rpm
   • 926 Nm at 3,000 rpm
   • 4-speed manual; rear-wheel drive
   • Top speed 330 km/h

   Accessed 2026-11-12