Formula 1 action will re-start this weekend after a month's summer break with the 12th race (of a record 20), the Belgian GP at Spa-Francorchamps.Not only is the hallowed circuit deep in Belgium’s brooding Ardennes forest the most feared on the trail but at seven kilometres is also the longest - by more than a kilometre - than the next longest, the UK's Silverstone. Spa’s wooded, hilly location ensures a capricious micro-climate which regularly has rain over one sector an none over the rest.LEGENDARY CHARACTERISTICSSpa’s high speeds and fast, flowing corners are legendary, although slower sections such as the La Source hairpin (Turn 1) and the Bus Stop chicane (T18/19) are equally challenging. It is also demanding on tyres which need to cope with extremely high lateral and extended longitudinal loadings, plus fearsome compression through foot-flat, left-right-left down-up Eau Rouge: loadings peak at 1000kg in a corner all F1 drivers agree presents the ultimate roller-coaster ride.All these factors combine to make the 44-lap race one of the calendar’s most unpredictable with ample scope for strategy to come into play – borne out by the fact that the race has been won only three times (2002, 2007, 2011) from pole in the past 10 years – with a three-stopper (laps five, 13 and 30) in 2011 proving victorious.Historically, the highest winning grid position is 10th, and a pace car has featured eight times in the same period.Cars are at full throttle for nearly 81% of each lap, the longest foot-flat stretch lasting 23 seconds. This makes Spa, along with Monza – which will host the Italian GP the followoing week before F1 embarks on a run of seven flyaways in Asia, the Middle East and the Americas – one of the quickest circuits of the year. That eight races remain after Spa, which has straddled August’s month-end for more than 20 years, proves how much the calendar has expanded: a decade ago only three races followed Belgium.FEW CIRCUIT CHANGESThe high speeds increase tyre temperatures, particularly when aggressive camber set-ups are adopted to maximise grip, while brakes come in for a real hammering at the Bus Stop where deceleration hits almost 6g as cars shed 200km/h from a peak of more than 300km/h in 2.13 seconds. The circuit demands 48 gear changes per lap, 2000 during the 90-minute race.Changes to the circuit since 2011 are few: apart from general tidying up and the laying of Astroturf between T10/11, the main change is that the white lines have all been repainted with a non-slip coating – incredibly, when Spa was dickied-up for 2011, the maintenance budget did not extend to FIA-approved skid-resistant paint!All the sport’s greats have won here over the years but only six have tasted Spa’s Champagne more than once; Red Bull’s reigning champion Sebastian Vettel took his sole Spa win in 2011. “I was very happy to have won there last year,” said the sport’s youngest (double) champion. “Spa offers every type of racing corner - ultra-fast, medium-fast and slow chicanes - that alternate with fast straights."The difference in altitude and unpredictable weather really make the track a big challenge – it’s one on which every racing driver loves to compete.”TOP CONTENDERS?Vettel is third in the title going to Spa, 122 points to the 164 of Ferrari’s Fernando Alonso who returns from the break secure with a win-and-a-bit in hand over Vettel’s team mate Australian Mark Webber on 124. McLaren’s Lewis Hamilton and Lotus' Kimi Räikkönen - 117 and 116 respectively - are the only drivers with a realistic chance of challenging the Spanish 2005/6 champion for the title. The Finn has an excellent record in Belgium and is the only top-fiver yet to win a race in 2012.None of this, however, means the rest are out of the running come Sunday: the super-smooth style of 2009 champion Jenson Button (McLaren) and the bravery of Lotus's coming man Romain Grosjean are ideal to meet Spa’s demands; Ferrari’s Felipe Massa, who has had two woeful seasons, knows he needs to pull his socks all the way up to stay with the red cars in 2013. Then there is Nico Rosberg, who celebrated in China after giving Mercedes its first win of the modern era. No Spa prixview can be complete without mention of Rosberg's team mate and compatriot Michael Schumacher: his F1 debut was here in 1991 and a mercurial relationship with the track developed, in turn dominating the race and being penalised for infringements. It's unlikely that, on current form, that he'll add to his six Spa wins, but he will celebrate the 21st anniversary of his debut with Jordan.He'll also become the second driver in history to contest 300 GP's.CAPRICIOUS WEATHER"Spa is like my living room," he said. "For me it's clearly the world's No.1 track. It's uncanny how I always seem to have special moments there - debut, first win, World championship victory, and many great races."Rain is predicted for Friday; indeed, Spa is seldom a dry race. Thus Pirelli’s tyre choice of hard (silver markings) and medium (white) – a combination last used in humid Malaysia – is likely to be academic with the intermediate (green) and rain (blue) options sure to see action. The race will start at 2pm South African time; qualifying from 2pm on Saturday. The Italian GP at Monza is scheduled for the following weekend.TAKE ON ONBOARD LAP OF SPA WITH KIMI RAIKKONEN: Stay with Wheels24 for the 2012 Belgian F1 weekend.