Brazilian GP – Characteristics of the Interlagos Circuit

A true natural layout, Interlagos winds over 4.309km and is renowned for its bumpy surface, even though the issue was partly addressed with a new resurfacing in 2004, and the track seems to have benefited from the same treatment for 2007. The physical demands of this circuit are particularly notable as it runs counterclockwise, subjecting drivers—and especially their necks—to forces opposite to what they usually experience. It is possible to overtake on this track, especially at the entrance to turn 1. The setup compromise generally tends to favor top speed on the straight rather than the best possible lap time: this gives drivers the opportunity to overtake… and not get overtaken during the 71 laps of the race.

Chassis

Aerodynamics: The different demands of Interlagos require almost opposite qualities from the cars. The first and last sectors consist mainly of long straights, where good top speed is essential to protect one’s position. This means that a relatively low level of aerodynamic downforce is needed there. However, the second sector consists of rather slow corners, which require a high load to provide grip during re-acceleration, braking, and cornering. Taking these two requirements into account gives rise to an optimal level of downforce aimed at achieving the best possible lap time. However, this optimum must also consider the other competitors. To defend one’s chances and attempt to overtake in turn 1, one must be fast at the end of the straight: therefore, downforce must be reduced. This means using a downforce level similar to that required for the Bahrain circuit.

Mechanics: It is difficult to find a good compromise in this field, once again due to the opposing characteristics of Interlagos. As with the aerodynamic sector, choices must be made and certain sectors prioritized. The most important corner at Interlagos is turn 12, which determines the top speed along the long main straight, uphill. Therefore, we pay great attention to the exit of this corner, even if it can generate a bit of understeer in the tight corners of the second sector. However, what is lost on this occasion is well worth the gains made by a good passage in the third sector. The second important parameter to consider is the track surface. Interlagos was traditionally very bumpy, but the new resurfacing done in 2004 allowed teams to use lower ride heights. The situation could be even better this year. The circuit does not put the brakes under severe strain but consists of three significant decelerations. The energy required in this area is comparable to Barcelona.

Tires: Interlagos includes few high-speed turns subjecting the tires to high lateral forces. Since the surface is not abrasive, fairly soft compounds can be used without issue. Consequently, Bridgestone will bring the soft and ultra-soft compounds from its Potenza 2007 range.

Engine

Performance: The long main straight of Interlagos demands a lot of power, and the longest period of full throttle exceeds 16 seconds. All engines must also be adapted to altitude constraints, as the circuit is located 800 meters above sea level. The lower atmospheric pressure results in a power loss of around 7%. Consequently, the 61% of the lap spent at full throttle corresponds to 57% at sea level (comparable to Budapest). This situation makes life easier for some mechanical components, like pistons. However, other elements, like the crankshaft, remain highly stressed. Progressiveness is also an important factor, especially in the second sector. Drivers use the lowest gears there, with sharp direction changes and quick actions on the brakes as well as the accelerator. The gradual delivery of power can have a real impact on the car’s balance, allowing drivers to use the optimal trajectory in this sector.

According to the ING Renault F1 Team