WRC

Rally Finland: Michelin preview

What better way could there be to kick off the second half of the 2004 championship than with the fastest and arguably the most furious round of the year: Rally Finland, won last year at an average speed of over 121 km/h! It's one they all want...

What better way could there be to kick off the second half of the 2004 championship than with the fastest and arguably the most furious round of the year: Rally Finland, won last year at an average speed of over 121 km/h!

It's one they all want to win. The locals because it's basically a national tradition: 50 wins for the home-grown stars and their Swedish neighbours from the 53 events organised since 1951. The non-Nordics, however, always dream of beating the specialists at their own game. Like Carlos Sainz, who first shattered their longstanding monopoly in 1990 (with Toyota), Didier Auriol (1992, Lancia-Michelin) and Markko Märtin (Ford), who notched up Michelin's 200th world class rally win in Jyväskylä in 2003, they know that a win on the '1000 Lakes' is worth its weight in gold on the curriculum vitae of a WRC driver…

Indeed, an enormous heart is indispensable here to go looking for those final tenths of a second that make all the difference at the flag. Launched at full song over this smooth, wide roller-coaster, it is essential for drivers to have a solid mastery of racing lines and to know just where to place their wheels - to the nearest millimetre - when lining up to take off at breathtaking speeds over the route's countless jumps.

Without a doubt, this is one for the specialists, and Rally Finland figures in fourth position in terms of Michelin's event by event successes since the creation of the World Rally Championship in 1973. On no fewer than 18 occasions (an outright record), the French firm's tyres have accompanied the winner of this Grand Prix of the forests onto the highest step of the podium. The challenge is to ensure irreproachable grip, response and steering precision over the high speed sections while at the same time being able to soak up dynamic vertical loads of up to 2 tonnes (one-wheel landings!) when coming back to Earth after the celebrated jumps (see the analysis of Citroën Sport's Jean-Claude Vaucard below…).

"Wear, on the other hand, is not a problem," points out Michelin Competition's Rallies Manager Aimé Chatard. "After Argentina three weeks ago, Finland's smooth gravel lends itself perfectly to the continuation of the new 'adapted' tyre quantities principle. For Finland, the individual driver quota is 70 tyres, up to 35 of which may actually be used. However, the more the WRC heads towards adopting this principle, the more it will be important to work closely with the organisers. This weekend, for example, we find ourselves faced with an additional loop of stages compared to what was initially planned, and the length of the groups of stages is not consistent. We are fully aware that the task of organisers is not easy, so working in osmosis with them can only be positive for the future..."

Jean-Claude Vaucard, high demands are made on tyres in all three planes in Finland: longitudinal, lateral and also vertical…

Jean-Claude Vaucard (Technical Manager, Citroën Sport): "It's true, tyres for Rally Finland must be capable of soaking up huge loads when they land after the infamous jumps since the cars can fall from as high as two metres. But this event has another specific feature: the corrugated portions over which tyres must not be too rigid 'vertically' in order to be able to contribute to the absorption of the vibrations generated by this type of surface.

"Once the soft top-coating has been brushed clear, the Finnish stages also produce rather high lateral acceleration values. Ironically though, it is not uncommon to benefit from even more grip in the damp since rain tends to pack the loose sand together.

"This phenomenon also applies to longitudinal performance, even though traction is not a key issue in Finland since there is less call to accelerate hard out of tight corners. There are however many long, fast portions that are covered in 4th, 5th and 6th gears. Here, the drivers look for first class straight-line stability and steering precision from their tyres, although the pattern must also be sufficiently open in order to ensure faultless traction and grip over the sandier parts. It's a case of finding the ideal compromise…"

Is it simple to choose the two types of pattern teams may nominate in the case of Finland?

J-C. V: "It's probably the easiest choice of the season as far as gravel rallies go. In recent years, we have used practically nothing but the Michelin ZA [a relatively open pattern] which we take in a selection of compounds to cover dry and damp conditions, although even here there isn't a big difference between the different options. The Michelin ZA covers close to 90% of situations, but we also nominate the more compact-patterned Michelin Z in case the going is particularly hot or dry. Its pattern is systematically re-cut however to make it into what we call a 'half ZA'. A standard Z is not at all suited to Rally Finland…"

What about wear?

J-C. V: "Wear isn't a problem, but you still have to think carefully when it comes to selecting compounds for such or such a group of stages. Choosing the most competitive solution is as critical here as anywhere else. There is one other thing though: the presence of concealed rocks on the inside of corners. People tend to imagine that the Finnish stages are perfectly smooth, but in fact they are not as clean as is commonly believed. The tyres' shoulders and sidewalls are therefore particularly exposed and pinch ruptures are always possible. If air is lost, the Michelin ATS fulfils its role, but an incident still consumes tyres…"

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About this article
Series WRC
Drivers Carlos Sainz , Markko Martin
Teams Citroën World Rally Team