Following the month-long summer break, Pirelli returns to action with the P Zero Silver hard tyre and P Zero White medium: a combination that has not been raced since the second grand prix of the season in Malaysia.

The conditions at the legendary Spa-Francorchamps circuit will be somewhat different however. The 7.004-kilometre lap is the longest of the entire year by some margin, and this is just one of the factors that can lead to extremely variable weather conditions, with a high risk of rain. Set within the Ardennes hills, Spa's geography also ensures that it has its own microclimate, meaning that it can often be raining on one part of the circuit but be completely dry on another part.

The track is renowned for its high speeds and fast corners. It is also challenging on the tyres, which have to cope with extremely high lateral and longitudinal energy loadings, thanks to fearsome compressions such as Eau Rouge: a corner that feels like the ultimate rollercoaster ride. This is why the two hardest compounds from Pirelli's range have been chosen, reflecting all the hard work that the tyres will have to do during the 44-lap race.

As Spa is such a long and variable race, there is ample scope for strategy to come into play, but tactics always have to be extremely flexible to cope with the potentially changeable weather conditions.

Paul Hembery: "The Spa circuit is a personal favourite of mine. I recently visited the 24-hour race there: the configuration of the track and the variety of the weather always seems to produce some great racing. From a tyre perspective, it's certainly one of the most demanding circuits that we face all year, because of the high speeds and extreme forces involved, which are often acting on the tyres in more than one dimension. The nomination of the hard and the medium tyres will allow drivers to push hard from start to finish, which is what Spa was designed for. The first half of the season began with the most close and competitive start to a year ever seen in Formula One's history, so I am looking forward to seeing how the rest of 2012 pans out, and which teams have made which steps forward over the summer break. Currently the grid is so closely-matched - particularly in the midfield - that it's impossible to predict."

Technical notes:

The cars are at full throttle in Spa for nearly 75% of the lap, which makes it one of the quickest circuits of the year together with Monza - which takes place the following weekend. The high speeds increase tyre temperature, particularly if an aggressive camber set-up is adopted to maximise grip.

With all the compressions at Spa, getting the ride height and suspension travel correct is vital as otherwise the cars could bottom out at some parts of the circuit. The tyre forms a vital component of the car's suspension, with the deformation of the rubber under load making up nearly half a Formula One car's total suspension travel.

Despite the famously high straight-line speeds in Spa, the cars run a medium downforce set-up in order to optimise grip through the many fast corners. Traction is a particularly vital factor at places such as La Source hairpin, where the mechanical grip from the tyres is key to a clean exit.

In the famous Eau Rouge compression each front tyre is subjected to a maximum peak of vertical loads of more than 1000kg.