The Ferrari 125 F1, initially called GPC, or Gran Premio Compressore, is the first single-seater built by the team from Maranello, and designed according to the specifications of the Formula Grand Prix. This will serve as the basis for the development of future Formula 1 cars, also taking part in three world championship Grand Prix in the 1950 Formula 1 World Championship.
The first drawings for a Formula 1 Ferrari, then Formula Grand Prix, date back to the postwar period by Giuseppe Busso, but when Gioachino Colombo switched from Alfa Romeo to Ferrari, he canceled Busso's project and decided to start from scratch.
In particular, perhaps because linked to outdated schemes, Colombo rejects the idea of adopting the De Dion bridge on the rear axle in favor of a pendular scheme.
Ferrari accepts this choice despite Nuvolari, who is often in Maranello, spoke of the great qualities of the de Dion bridge which he himself had tested on pre-war Auto Union Type C cars. This difference of opinion will push Busso to leave Ferrari going back to Alfa Romeo.
The engine, born from the hand of Colombo, is a twelve-cylinder 1.500 cm³, supercharged with a single-stage Roots compressor (the maximum formula in force is 1.500 cm³ for supercharged engines and 4.500 cm³ for aspirated engines).
The frame of the longitudinal and cross members type, made by Gilco, has a very short wheelbase which gives it excellent agility.
The fine-tuning of the twelve-cylinder, commissioned by Ferrari himself, will however be extremely complicated from the start. In fact, especially in the supercharged version, it will prove to be bulky, heavy, penalized by excessive fuel consumption and by a chronic loss of power at high revs due to compressor drag.
In theory the V12 would have been able to reach a maximum of 10.000 rpm, but in real terms will never exceed 7.500 also due to the lack of adequate ignition.
About a year after its first appearance, an updated version of the 125 F1 will make its appearance, equipped with two Roots compressors and two gear-driven camshafts per bank, and both wheelbase and fuel tank will be modified, later more capacious, to challange Alfa Romeo and Maserati, which instead have much more powerful engines.
Further modifications will be introduced for 1950 by engineer Aurelio Lampredi, who will finally abandon the pendulum scheme in favor of a De Dion rear axle and arrange the gearbox, now four-speed, in block with the differential. The engine will be raised to 280 horsepower, and the wheelbase will be modified again. Also from the aesthetic point of view, numerous changes will be made that led it to resemble the future 375 F1.
The first appearance of the 125 F1 took place in Turin, on 5 September 1948, on the Valentino Circuit, in the 19th Italian Grand Prix, with three cars entrusted to Giuseppe Farina, Raymond Sommer and Prince Bira. Despite Farina's retirements due to the damaged radiator, and Bira’s due to the transmission, Sommer's surprising third place behind Jean-Pierre Wimille's victorious Alfa Romeo 158 and Gigi Villoresi's Maserati convinces Enzo Ferrari to continue development of the Grand Prix category cars that the Modena manufacturer was inclined to abandon due to heavy expenses.
The first success of the 125 F1 came two races later, on the occasion of the Grand Prix raced on the Garda circuit, won by Farina. It represented Ferrari’s first F1 win.
1949 saw the passage to Ferrari of Ascari and Villoresi, and the sale of two 125s to the drivers Peter Whitehead and Tony Vandervell, future owner of Vanwall.
Renaming it Thinwall Special his 125, Vanderwell will make it one of the first examples of a sponsored car: this name, in fact, will advertise his bushing factory from which Ferrari itself supplies.
In this same year, in Monza, Ascari's first victory of the season was recorded, thanks to the new 125 with two-stage compressor, which will also be repeated in Switzerland and the Netherlands.
But the most important event will be the defeat that Villoresi will suffer at the hands of Louis Rosier's Talbot, on the occasion of the Belgian Grand Prix. In the lead for most of the race, Villoresi will be forced to stop in the pits for refueling; unlike the Frenchman's Talbot, which does not have a compressor and therefore consumes less, it is not necessary to stop until after having crossed the finish line victorious.
This event will favor the choice of Ferrari for the abandonment of supercharged engines. In the inaugural season of the Formula 1 World Championship, Ferrari will desert the opening race at Silverstone but will show up in Monaco with Ascari, second at the finish line, and Villoresi, retired due to transmission problems. The Formula 1 career of the 125 F1 within the Scuderia Ferrari will end in Monaco but will continue thanks to the private team of Peter Whitehead who will finish third in France and seventh in Italy. The following year, Whitehead would still drive the 125 F1 without however reaping significant results.
Here also ends the racing career in the top formula of 125 F1, which will continue to appear in minor races by private drivers.
The 125 F1, the pioneer of all Ferrari's single-seaters, concludes its journey with two podiums out of a total of five races, with a second place in Monaco for Alberto Ascari, and a third place at the Grand Prix of France by British private driver Peter Whitehead.