Dakar : BFGoodrich - Preview
With seven previous Dakar Rally wins to its name, including five with Mitsubishi, BFGoodrich is poised to set off on the African trail once more on January 6 for the 29th running of the world's most famous rally-raid, the Euromilhoes Dakar.
year again, all the top teams have placed their confidence in BFGoodrich in their bid for victory, while the amateur runners will be counting on the inherent strength of the firm's products to take them all the way to Dakar. The 29th Dakar Rally is scheduled to start in Lisbon on January 6 and features a total length of 8,696km, including 5,010km against the clock, the equivalent of practically a full World Rally Championship campaign packed into a mere 15 days!
Different surface types
Continuing the parallel between the Dakar and the WRC, which saw BFGoodrich claim a landmark clean sweep of 16 wins and both titles in 2006, the Dakar route also takes in a long list of different surface types that tyres must be capable of taking in their stride.
Yet to cater for the sharp stones that litter the mountain tracks of Morocco, the sandy reaches of Mauritania which can conceal treacherous rocks and the hard- packed, low-grip laterite trails of Senegal, the regulations only permit priority drivers to use a single type of tyre.
"Following tests in Morocco and Tunisia last October and November, the factory Mitsubishi, VW and BMW/X-Raid teams opted for the BFGoodrich Rock T/A, the tyre which won the 2006 Dakar on the Mitsubishi Pajero of Luc Alphand," says BFGoodrich rally-raid tyre technician Dominique Bravy.
"On the Dakar, it's the casing that bears the brunt of the punishment and the repeated knocks tyres need to soak up, so our work focused on enhancing the strength of the Rock T/A. It's important to realise that the cars can tip the scales at as much as 2.5 tonnes with a full tank and individual tyres sometimes have to withstand dynamic loads of up to 3 tonnes, when landing after a jump for example."
Given that priority drivers are only permitted to use one type of tyre, the trick lies in adjusting pressures in order to adapt them to the different types of terrain competitors cross. The rocky tracks of Morocco call for high pressures of about 3 bar to ensure maximum strength, while for the sandy stages of Mauritania the drivers must run pressures as low as perhaps 1.6 bar with a view to increasing the area of the contact patch.
"The use of systems that allow tyre pressures to be raised or lowered from the cabin has been banned for 4WD vehicles, so adjusting pressures can seem costly in time terms. The crews must also remember to re-inflate their tyres after crossing sand, otherwise they run the risk of puncturing."
Punctures are the sworn enemy of rally-raiders. However, because of the distances involved and the searing temperatures, tyres cannot be equipped with the sort of run-flat mousse that has become a familiar sight in modern world championship rallying.
Meanwhile, today's rally- raid prototypes are becoming increasingly competitive and quick, and the scrap between the top teams is fiercer today than it has ever been. Over a competitive distance of 5,010km, punctures are inevitable; the target is to make they are as infrequent as possible.
"Everything is relative though," explains Dominique Bravy. "To change a wheel takes maybe three minutes, that is to say a mere 0.09% of the 53 hours and 47 minutes spent on the stages by the 2006 winner. But there's no getting away from the fact that picking up a puncture – or even two or three – on a stage can sap morale."
The majority of punctures concern the rear right- side tyre. Rear tyres effectively have the toughest job in rally-raids and, given the size of the cars involved, the right side is the side the drivers are the least aware of.
"They might think their rear right tyre is on the stage but in reality it often strays onto the rockier edge of the stage," points out Dominique Bravy. Certain factory cars are equipped with puncture detection systems of the type used during the Le Mans 24 Hours. Cars are also authorised to carry up to four spares.