Tech file - Indianapolis

The Formula One circuit constructed within the boundaries of the world famous Indianapolis Motor Speedway, the venue of the upcoming US Grand Prix, may look simple on paper – but as always in Formula One, appearances are very deceptive.

The tight, technical infield layout is combined with one of the longest straights of the year, and this demands opposing characteristics from the car: impeccable low speed grip and handling combined with low downforce levels and a strong top speed. The famous banking and yard of bricks lend the circuit a unique flavour, but a good lap-time is built in the twisting infield, where the drivers need to be neat and precise in their driving throughout the 73-lap race.

Downforce: Indianapolis is a circuit composed of two radically different halves. Ideally, the teams would run higher downforce levels than they do in reality, in order to improve grip through the twisting infield, particularly under acceleration and braking. However, the long straight leading to turn 1 represents a legitimate overtaking opportunity, and this complicates the choice of downforce level. The car’s top speed must be sufficient to allow the driver to pass competitors in front, and indeed to defend his position against competitors behind. Wing levels are therefore calculated to provide a competitive top speed of around 320 kph (similar to that achieved in Canada), while generating sufficient downforce to be competitive through the infield. The engineers will tune their choice of downforce level during the weekend, according to the top speeds reached by other competitors.

Mechanical: Much as in Canada, the car’s in-corner performance is dictated primarily by the mechanical set-up of the car, rather than dominated by aerodynamics. This is because many of the corners are taken at low speed, in second or third gears. The long sweep of turns 3, 4 and 5 is taken as a single corner, and requires good front-end stability to give the driver confidence, much like in turn 11, where the exit is the critical factor as the drivers do not lift off again afterwards until they begin braking for turn 1.

Strategy: The Canadian Grand Prix marked the first time in 2007 that a car running anything other than a two-stop strategy reached the podium (Wurz did so by making a single stop). This was thanks in large part to the unusual circumstances of the race, with numerous safety car periods. At Indianapolis, teams are likely to adhere to this pattern, aiming to spend the greatest possible percentage of the race on the most race-worthy compound. Like in Canada, fuel consumption and the lap-time penalty for carrying additional fuel are relatively low at this circuit, meaning it is possible to run a ‘rearward-biased’ strategy (stopping later than the 1/3 and 2/3 distance) without overloading the tyres, or incurring too great a time penalty in qualifying.

Tyres: The Bridgestone Potenza tyre compounds available for this weekend are the ‘soft’ and ‘medium’ options from the 2007 range. This is the second time these compounds will be raced, the first having come in Melbourne. The compounds are a step harder than those used in Canada last weekend, reflecting the higher lateral loads encountered on the infield and on the banking, which require the tyre to work harder than in Montreal.

Engine: The engines spend just 59% of the lap at full throttle, below the season average, which might induce people to think that this circuit is relatively easy for the engines. However, the track also includes a full throttle period which lasts for around 22 seconds (from the exit of turn 11 to the braking zone for turn 1). This is the longest of the season, and continuous periods at full throttle put the engines under particular strain. The engine also needs good torque characteristics to launch the car out of the numerous slow corners, and this is an area in which the RS27 is particularly strong.