WRC

Swedish Rally: BFGoodrich preview

Ice Age 2 This year marks BFGoodrich's second visit to the Swedish Rally after the g-Force Ice took Ford's Marcus Grönholm to victory in Karlstad in 2006. This year, the Finn will be hunting for a fifth personal success on one of the calendar's...

Ice Age 2

This year marks BFGoodrich's second visit to the Swedish Rally after the g-Force Ice took Ford's Marcus Grönholm to victory in Karlstad in 2006. This year, the Finn will be hunting for a fifth personal success on one of the calendar's most spectacular shows which sees the WRC cars reach speeds of up to 200kph on sheet ice. This year again, the stud-spangled g-Force Ice promises to take front stage.

Ice-cool drivers, half-frozen spectators and cars dancing on sheet ice, brushing snow banks and crossing dark forests at vertiginous speeds with the occasional elk looking imperturbably on?

These are the cliché images of the Swedish Rally, yet the true stars of the show are the tiny tungsten tips inserted in the tyres which strike the ground 17 times every second at 120kph to provide the necessary traction and grip to keep the cars on the icy lanes.

Each g-Force Ice bristles with 384 tungsten studs. But metal and rubber have radically different properties and successful bonding the two is dependent on the quality of gluing technique. For this particular job, BFGoodrich calls on the services of a Swedish subcontractor to insert and glue the studs one-by-one in the orifices of the tread blocks. The g-Force Ice tyres are made in France before being transported to Sweden where the gluing process takes place. Preparing each g-Force Ice tyre demands approximately one hour's work.

The studs used for the Swedish Rally must comply with strict FIA regulations which specify a maximum length (20mm), a maximum weight (4g) and other key dimensions. However, the proportion of the stud that protrudes from the tyre can be modified as a function of both the conditions (snow, pure ice, frozen dirt) and the type of ice.

There are effectively numerous different types of ice, just as there are different types of sand on the Dakar. Depending on whether the ice is very cold (-20°C), simply cold (-5°C) or thawing (0°C), the amount of grip available can be very different. To see for yourself, try taking an ice cube from a freezer. To begin with it sticks to the fingers but after a few minutes it becomes so slippery that it is difficult to keep a hold of it.

BFGoodrich's technicians will consequently use the information supplied by their route observers and the weathermen to help the drivers choose their tyres. In 2006, Marcus Grönholm paved the way for his win by choosing the 'long stud' option on Day 2.

A MILLIMETRE - The difference between the length of the visible part of the stud between the g-Force Ice 'normal stud' and 'long stud' options is less than 1mm. Although tiny, this difference can be felt at the wheel.

NEW PROCESS - A new process for gluing the studs in the tread blocks was used this year to enhance the durability of the g-Force Ice tyres.

TUNGSTEN - In Swedish, tung sten means 'heavy stone'. Tungsten, the hardest and heaviest metal on Earth, features in the composition of the studs used on the Swedish Rally. Its melting point is 3,410°C!

537 METRES, 107KG - A full quota of 70 g-Force Ice tyres represents 537m of tungsten alloy that tips the scales at approximately 107kg! If the studs of the 70 tyres available in Sweden for the 16 drivers who must comply with the quota system were laid end to end, they would stretch 8.60km!

50 STUDS - At any given moment, the rally cars stand on just 50 studs (13 per wheel). It is these 50 studs that are entrusted with transmitting the 300hp of the WRC cars to the ground.

1,988 TYRES - It is the company Däckproffsen that was entrusted with studding the 1,988 BFGoodrich g- Force Ice tyres available for Sweden and Norway (not including the tyres used in testing).

TESTING RESTRICTIONS - Testing for Sweden and Norway is limited by the FIA. Teams may only test onsite four days a year, in one country or the other. Citroën and Ford tested at the beginning of December, while Subaru tested the g-Force Ice tyres early in February.

207 S2000 - Sweden marks the world debut for the Peugeot 207 S2000 which will run on BFGoodrich g- Force Ice tyres of the same dimension as those used by the WRC cars.

g-FORCE STUD - BFGoodrich has profited from the Swedish and Norway Rallies to launch a studded road car tyre on the Nordic markets: the g-Force Stud. This new tyre joins the winter range which already features the Winter G and the Winter 2 T/A.

-credit: bfg

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About this article
Series WRC
Drivers Marcus Gronholm
Teams Citroën World Rally Team