The regulatory revolution scheduled for 2026 pushed almost all teams to halt work on the 2025 car during the summer, redirecting resources towards the project for the new era. This was not the case for Red Bull, which continued to introduce updates well into autumn, keeping Max Verstappen in the fight for the world championship until November. Here are the main stages of the development of the RB21.
The floor
Red Bull was the team that produced the highest number of floors overall, reaching a total of six. After the launch specification, the first updated version debuted during testing, followed by the changes introduced in Miami, the updates brought for the Austria–Silverstone double-header, the Monza floor, and finally the version introduced in Mexico. The sheer volume of new components raised concerns within the Milton Keynes team about how to remain within the budget cap, especially with the 2026 car already under development.
The team therefore tried to optimise resources, modifying only certain sections of existing floors in order to avoid constantly producing entirely new ones, whose cost would have been close to half a million dollars per package.
The floor introduced at the Italian Grand Prix was undoubtedly a turning point in Red Bull’s season. This update allowed the car to run at a lower ride height, extracting more aerodynamic load from the underbody and giving fresh momentum to the RB21. By contrast, the update introduced in Mexico City proved short-lived, as it was removed after the Brazilian Sprint due to difficulties in finding a satisfactory setup.
Front wing
The Milton Keynes team paid close attention to the front end of the car in an effort to meet Max Verstappen’s requests. The Dutch driver is well known for preferring a very sharp front end, with a balance shifted more towards oversteer in order to help the car rotate more easily through corners. It therefore comes as no surprise that Red Bull produced as many as five different front wing versions, compared to the two usually offered by rival teams.
The launch version already evolved during pre-season testing, followed by the Spain specification, developed to comply with the new deformability criteria imposed by the FIA. During the summer, two more front wings debuted at Spa-Francorchamps and Zandvoort, followed by a final update in Singapore. Red Bull did not focus solely on geometry, however, also optimising the carbon fibre lay-up to recover some of the flexibility lost following the Barcelona technical directive.
Details make the difference
The Anglo-Austrian team developed the RB21’s aerodynamics in a comprehensive manner, leaving no area overlooked. In Belgium, for example, the team refined the fairings around the front suspension arms, while at Suzuka and Imola changes were observed at the rear of the car.
Still at the rear end, between Spa and Baku, Red Bull introduced changes to the rear wheel assembly flaps, aiming to protect the diffuser from turbulence generated by the driven wheels.
One of the most important updates of the year was the new low-downforce rear wing, which made its debut at Silverstone. With this solution, the team addressed a significant weakness from previous seasons, when it lacked wings suitable for high-speed circuits and suffered from higher drag. In 2025, the RB21 could rely on a true low-downforce configuration, which made it the most aerodynamically efficient car on the grid.
Cooling
One of Red Bull’s main issues in 2024 was a tendency to overheat, a consequence of the extreme architecture of the RB20. The situation improved in 2025, but this area still required ongoing attention. At Imola and Spa, for example, the radiator inlets on the sides of the cockpit were revised, while in Japan, Bahrain, Saudi Arabia, Singapore and Mexico a series of updates affected the engine cover and cooling louvres.
In some cases, the focus was not purely on heat dissipation, but also on improving the aerodynamic interaction with the rear wing.
Significant work was also carried out on the cooling ducts and brake ducts. The rear assemblies were revised at Suzuka and Imola, while at Budapest and Mexico City the changes concerned the front axle. In this area, the Milton Keynes squad sought inspiration from McLaren, whose cooling assemblies were one of the factors behind the strong tyre degradation management of the MCL39.
Overall, Red Bull was the undisputed leader in development throughout the 2025 season, but the initial technical deficit proved too large and ultimately became the main reason why the world championship slipped away at the final race.
The RB21 development timeline
- Australia: front wing, floor (already at testing)
- Japan: engine cover, rear brake cooling, rear suspension arm fairings
- Bahrain: front wing flaps, engine cover cooling grilles
- Saudi Arabia: engine cover, beam wing
- Miami: floor
- Imola: side radiator inlets, rear brake ducts, rear suspension arm fairings
- Monaco: rear wing, beam wing, front suspension modifications, enlarged front brake ducts
- Spain: front wing
- Austria: floor
- Silverstone: floor, rear wing
- Spa: front wing, front suspension fairings, side radiator inlets, bodywork, rear wheel assembly aerodynamics
- Hungary: front wing flaps, front brake ducts
- Zandvoort: front wing flaps
- Monza: floor, front wing flaps
- Baku: rear wheel assembly aerodynamics
- Singapore: front wing, engine cover
- Mexico: floor, engine cover and bodywork, front brake cooling ducts
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