RENAULT R25

   In 2005, thanks to the Renault R25 single-seater and the talented young Spanish driver Fernando Alonso, Renault finally achieved the world championship title with its own car, a title unsuccessfully pursued in the early 1980s with turbo cars entrusted to various drivers, including Jabouille, Arnoux, Prost, Warwick, and many others. The Renault R25 marked the first world championship title for a single-seater with a French license since the triumph of the Matra MS80 in 1969. The president of the Renault F1 team, Patrick Faure, once again entrusted capable Italian manager Flavio Briatore with full management of the team, which in 2005 still included a strong lineup of excellent engineers. The team’s Executive Engineer was the Briton Pat Symonds, while Northern Irishman Bob Bell from Belfast was Technical Director, with Englishman James Allison as Deputy Technical Director. The British engineer Tim Densham served as Chief Designer, working alongside newcomer Martin Tolliday in the role of Project Leader. In 2005, Tad Czapski was Technology Director, while his former position of Head of R&D was now covered by another new arrival, Robin Tuluie. The increasingly important role of Head of Aerodynamics remained in the hands of Italian Dino Toso, while Frenchman Bernard Dudot, the father of all Renault’s legendary engines since the 1.5-liter turbo V6 of 1977, was still involved with the team as Engine Technical Director.

RENAULT R25, Fernando Alonso
Montecarlo, Monaco GP 2005

   The new R25 was presented on February 1 at the Grimaldi Forum in Montecarlo, in order to bypass French law that prohibited the display of tobacco sponsor logos, Mild Seven still adorned the car’s livery in 2005. However, the week before, the car had already been unveiled during its first outing at Spain’s Ricardo Tormo circuit in Valencia. At first glance, the car seemed a simple evolution of the previous R24, but it featured significant differences. The R25 represented the fifth year of a technical concept launched by the team in 2001, initially based on a very wide-angle V engine, designed to lower the car’s center of gravity and provide an aerodynamic advantage. In 2004, Renault definitively abandoned the 111° V10 in favor of a much narrower 72° V engine and, even though 2005 was the final year of V10 engines, Renault developed an entirely new design. Project leader Axel Plasse, under the supervision of Technical Director Rob White, designed the new RS25 V10 at the French facility in Viry-Châtillon. It featured a significantly lower center of gravity and aimed for reliability over 1,400 km, a nearly doubled lifespan, while maintaining the power and weight of its predecessor, thanks to new alloys and improved component casting techniques. The new French V10 delivered between 800 and 900 hp, reaching up to 19,000 rpm, slightly less than the Mercedes engine used by McLaren, but considerably lighter and above all more fuel-efficient, allowing for a 98 kg fuel tank compared to McLaren’s 106 kg, as well as a significantly lighter cooling system. Equally important was the new electronic management system, a field that was advancing rapidly at the time, capable of processing about ten times more data than the previous system.

RENAULT R25, Giancarlo Fisichella
Melbourne, Australian GP 2005

   A key part of the car’s design philosophy was to create immense rear-end rigidity for maximum stability, with the narrow-angle engine being integral to this concept. Two carbon-fiber struts connected the front of the gearbox to the chassis behind the cockpit to further increase stiffness. The gearbox itself was crucial to achieving the required structural rigidity: the R25’s titanium gearbox case was long and relatively heavy, ensuring the desired rear-biased weight distribution. The R25 was also the last Renault Formula 1 car to use a 6-speed gearbox before the mandatory switch to 7 speeds in the following season. The engine’s favorable torque curve gave the car excellent drivability which, combined with outstanding traction, ensured lightning-fast starts and top-level performance in slow corners. Engineers at Enstone, in Oxfordshire, England (Renault’s British base), deliberately shifted more weight to the rear axle than any rival team to maximize traction, especially in combination with Renault’s Michelin tires, which featured highly flexible sidewalls. This unusual weight distribution and massive rear-end rigidity gave the car very distinctive handling, tending toward understeer with the front tires lightly loaded, but it suited Alonso’s unique driving style, enabling him to deliver strong performances under all conditions.

RENAULT R25, Fernando Alonso
Nürburgring Gp-Strecke, European GP 2005

   The R25 featured a relatively simple front wing and brake ducts, at a time when others, notably McLaren, were beginning to heavily sculpt these components. The front wing chord area was not at the maximum allowed and had a simple design, as much of the downforce had to come from the rear of the car. Indeed, not all available airflow at the front was used to generate front downforce but rather to channel more flow toward the rear. After Sauber introduced the “twin keel” in 2001, Renault debuted its own interpretation with the R25: a V-keel, an elegant solution that combined the advantages of both systems while retaining the team’s preferred front suspension layout, which had been significantly revised with wishbones raised as high as possible from the ground. During development, however, the team realized that rear tire wear was somewhat excessive. From the San Marino Grand Prix onwards, the front wings sported outer upper flaps to provide the additional required downforce without substantially altering airflow toward the bargeboards and rear. The sidepods were rather pronounced at the front and featured a set of ventilation slits beside the engine cover, allowing hot air from the radiators to exit more progressively and smoothly, in place of the traditional chimneys used by other teams.

RENAULT R25, Fernando Alonso
Nürburgring Gp-Strecke, European GP 2005 

   The new sporting regulations, valid only for that season, prohibited tire changes during races, meaning pit stops were exclusively for refueling (which would only be banned from 2010 onwards). This ban on tire changes proved decisive during the season, making Ferrari’s Bridgestone tires uncompetitive compared to Michelin’s, and allowing the R25, entrusted to Fernando Alonso and Italian driver Giancarlo Fisichella, to achieve excellent results right from the start. Fisichella won the opening race of the season, followed by three consecutive victories for Alonso. The Italian also scored two more podiums, as well as several points finishes. Alonso, meanwhile, enjoyed an outstanding season, helped by the excellent reliability of the R25, which finished outside the points only twice in 36 starts. With 7 victories and 8 additional podiums, Fernando Alonso was crowned World Champion with 133 points, while Renault won the Constructors’ Championship with 191 points, fighting until the end with McLaren-Mercedes, who scored 182. A notable fact: the R25 was the first Constructors’ Championship-winning car since 1991 not designed by either Adrian Newey or Rory Byrne.