WRC

Rally of Portugal 2001 - Michelin preview

2001 World Rally Championship Round 3: Rally of Portugal (March 8th - 11th 2001) Looking for a sign This weekend sees the World Rally Championship make its first appearance of the season on what is by far the most frequently encountered...

2001 World Rally Championship
Round 3: Rally of Portugal (March 8th - 11th 2001)

Looking for a sign

This weekend sees the World Rally Championship make its first appearance of the season on what is by far the most frequently encountered surface of the year, namely gravel. For with the exception of the three clear asphalt rounds (Catalunya, Corsica, Sanremo) and the two winter classics (Monte Carlo, Sweden), the calendar is in its majority made up of events run on the loose.

It should be remembered however that the term 'gravel' covers a broad spectrum of

surface types since each event features its own specific characteristics. For example, the punishing stages of Greece and Cyprus have little in common with the giddy roller coaster ride of Finland, while the interminable, high speed portions in the searing heat of the Safari mark a stark contrast with Britain's muddy forests!

The Rally of Portugal essentially comes under the category of 'smooth gravel', although there is a certain contrast between the sandy stages in the northern part of its route and the rockier tracks to the south.

Moreover, the Portuguese round is eagerly awaited each year since it is seen as an early pointer to the relative competitiveness of the top cars on the loose. Twelve months ago, for example, 2nd place for the Peugeot 206 WRC-Michelin and Marcus Grönholm revealed the French machine's potential on the loose and the car went on to clinch the Manufacturers' title barely eight months later.

Looking back, it is conceivable that by narrowly failing to win last year's event actually played into the hands of the reigning World Champion. For it is interesting to note that since 1990 only one driver has gone on to take the world crown after winning in Portugal. That was Tommi Mäkinen in 1997. Next Sunday, the winner of the 2001 event will no doubt be hoping this unwritten rule will again be snubbed this time round!

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On the technical front

Tyres and the World Rally Championship

Like any tyre (car, truck), a World Rally Championship tyre has to fulfil a certain number of functions: grip, absorb, steer, transmit, resist. To be competitive, it must of course combine all these roles. However, the specificity of each round tends to put the spotlight on one or sometimes two of these functions…

Grip

Rally of Portugal : Traction

o Portugal's mix of sandy stages in the north and hard base-rock on Leg 2 makes efficient traction vital. Good traction is also essential for the treacherous film of clayey mud that forms in the Arganil region in the wet. And the chances of rain are higher this year due to the event's earlier date. It should be remembered that the 300+bhp of today's WRC cars passes to the ground via the tyre's contact patch, a mere 140cm² per wheel. To ensure all this power is transmitted as efficiently as possible, a long list of factors influence tyre specification…

When grip is at a premium, the higher the per-square cm load on a tyre, the more it bites into the ground and the better it transmits the power. This is why snow tyres are so narrow. Similarly, the narrow option Michelin ZE has been producing stage-winning performance on the loose since its launch in November '99.

o Meanwhile, in addition to dealing with the forces generated under acceleration and braking, the tyre's structure is designed to constantly stabilise the contact patch. Along with compound, it is effectively what goes on inside the casing that differentiates a Portugal tyre, say, from a Safari tyre.

o The other key parameter is the tread pattern, the mission of which is to clear the top layer of loose in search of a more stable base. At the same time, the layout of the tread blocks is conceived to favour traction both in a straight line and in corners. This is the reason for the 'rounded' form of Michelin's WRC gravel patterns.

The rules dictate however that teams can use a maximum of just two patterns to cover the exceptional variety of conditions they can face in Portugal.

Grip is generated by the reaction of the rubber's molecules over the unevenness of the ground. The tyre's pattern and dimensions contribute to grip by optimising the contact between the tread and the road.

Absorb

The properties of tyres and the air they contain form an integral part of the vehicle's suspension, especially since the tyre is in the front line when it comes to soaking up obstacles on the road.

Steer

A tyre must be capable of responding instantly and as accurately as possible to the driver's instructions via the steering wheel. The construction and compound of the tyre directly influence the quality of this response.

Transmit

Not only must the tyre transmit the vehicle's power to the ground, but its construction and pattern must also enable it cope efficiently with the effects of torque, be this positive (acceleration) or negative (braking).

Resist

Despite suffering repeated aggression due to the extreme running conditions (long distances at high speed, high temperatures, long groups of stages, rough ground), the tyre must conserve its performance characteristics over time.

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Michelin will have a total staff of 24 for the Rally of Portugal. The total number of covers available for the event is 3,540 carried in 8 semi-trailer workshops. All are fitted with Michelin's ATS system (Appui Temporaire Souple). These figures do not include those teams supplied and serviced by Michelin Portugal.

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About this article
Series WRC
Drivers Tommi Makinen , Marcus Gronholm