Spa-Francorchamps is one of the toughest circuits on the GP2 and GP3 calendars, not only having the longest lap at 7.004 kilometres, but also lots of high-speed corners that place multi-directional forces on the tyres. The P Zero Orange hard and P Zero Yellow soft tyres have been selected for GP2 (a step softer than last year, when the hard and medium was chosen) while the medium tyre is nominated for GP3.

Spa-Francorchamps is one of the most technically demanding tracks on the GP2 and GP3 calendar. The flowing track contains a wide variety of exhilarating corners as well as fast straights but with the lap being so long, there are many variables to contend with in just one lap, let alone the whole race.

The GP3 drivers have been nominated with the medium tyre, the same as 2014. However, the 2015 GP3 tyres are all a step softer than their 2014 equivalents - and this year, Saturday's GP3 race is also longer.

The GP2 drivers will once again have the hard tyre but this time accompanied by the soft as opposed to the medium, which was used in 2014. This will provide extra degradation to encourage even closer racing this year.

The weather provides a big challenge at Spa as it can often change mid race or even mid-lap, and rain is expected at some point over the weekend. This can have a dramatic effect on the race causing more pit stops and tyre changes, so strategy and speed of reaction is key.

Pirelli's racing manager, Mario Isola says: "We now return to one of the toughest circuits on the calendar, Spa, after the summer break. This circuit is particularly testing on the tyres as each lap is so long with a wide-ranging set of demands. The weather can be a real game-changer at Spa and it is likely we will see some rain over the weekend. This often makes for a very exciting race, where strategy makes a real difference. Any mistakes are magnified by the length of the lap: if the wrong tyre choice is made, the drivers have to spend a comparatively long time on it before getting the chance to change.

"We're expecting quite a big difference in terms of lap time between the hard and the soft in GP2, which should have an interesting effect on strategy. This also means that the soft tyre will be used for qualifying: the drivers will then have to make the best of these tyres for the rest of the weekend.

"In GP3, Saturday's feature race is now longer than the sprint race on Sunday: this clearly has a significant effect on tyre usage and management."