Given that the first version of the newly built 12-cylinder record-breaking car based on the W 125 Grand Prix car had clearly failed to meet its intended targets at the premiere of "Record Week" at the end of October 1937, the unfortunate situation arose for Daimler-Benz that, under the given circumstances, the next opportunity for rehabilitation did not open up until autumn 1938 - more than six months after the International Automobile and Motorcycle Exhibition (IAMA), the most important showcase for the domestic automotive industry.

In addition to some minor measures to increase mechanical stability, detailed improvements were made to the mixture supply system in the short time available.

During the 1937 record week, the visually harmonious fully streamlined body of the W 125 record-breaking car had lacked aerodynamic efficiency.

For record runs over short distances, this made it possible to dispense with a classic coolant radiator, which always had a negative impact on the aerodynamic balance due to its cooling air requirements and the necessary openings.

The now significantly lowered front end of the car produced much higher downforce values, which resulted in better driving stability.

Even on his first morning test run, Rudolf Caracciola was spontaneously thrilled by the car's tracking stability, and the V12 engine also delivered its full power.

Averaging the outbound and inbound legs, the type of measurement prescribed by the regulations, Caracciola achieved a sensational 432.692 km/h over the kilometre and 432.361 km/h over the mile, both with a flying start.

According to the latest measuring methods, the newly designed body of the 12-cylinder record-breaking car from 1938 had a drag coefficient of only Cd = 0.157, which is impressive even by today's standards.

[4] Rudolf Caracciola's record of 432.7 km/h (268.9 mph) over the flying kilometre on 28 January 1938, remained the fastest ever officially timed speed on a public road until broken on 5 November 2017 by Koenigsegg in an Agera RS driven by Niklas Lilja, achieving 447.2 km/h (277.9 mph) on a closed highway in Nevada.It also was the fastest speed ever recorded in Germany until Rico Anthes bested it with a Top Fuel Dragster on the Hockenheimring drag strip.

This record breaking run was made on the Reichs-Autobahn A5 between Frankfurt and Darmstadt, where onlookers were rattled by the brutal boom of the side spewing exhaust stacks as the silver car hurtled past.