WRC

Rally Australia: Michelin preview

Australia's brainteaser The small, marble-like stones that carpet the stages around Western Australia's capital Perth have long been a brainteaser for drivers and tyre firms alike. The precarious grip they offer also accounts for another of the...

Australia's brainteaser

The small, marble-like stones that carpet the stages around Western Australia's capital Perth have long been a brainteaser for drivers and tyre firms alike. The precarious grip they offer also accounts for another of the event's challenges: keeping clear of the trees that line the ultra-fast tracks, ready to punish any driver who strays even the slightest bit off line. When it was organised later in the calendar, both world titles were frequently decided here. This year however sees the event revert to its original September date, which means competitors will have to take onboard another parameter: a stronger likelihood of rain which can make the stages as slippery as a skating rink. Once again, the savoir-faire of Michelin, winner of 11 of the 15 Rally Australias organised to date, promises to be a valuable ally...

Just under a year ago, Peugeot-Michelin and Marcus Grönholm collected their third consecutive success together in Australia. For once, however, both the Manufacturers' and Drivers' crowns had been sewn up before the WRC's arrival in Perth for the penultimate showdown of 2002.

This year, the trip to the other side of the planet takes place some two months earlier, with six title candidates grouped within just twelve points of each other at the sharp end of the Drivers' championship (a win is worth ten units), a vivid pointer as to how open this year's campaign is proving. And how could it be otherwise given that five different drivers have won the nine rounds so far, while on the Manufacturers' front, the spoils have been shared by no fewer than four makes, including three of Michelin's partners?

Organised this year ahead of a mini-tour of three asphalt events before the series concludes with the gravel of Wales, Rally Australia clearly holds a strategic place in the 2003 calendar and the battle for supremacy promises to be particularly fierce. Its stages however represent a unique challenge and, as if the region's famous 'marbles' weren't slippery enough in the dry, rain could make them more treacherous still, which makes the task of the tyres just as critical whichever way the weather turns.

But here like elsewhere, Michelin's partners, who currently lead both championships, will be able to benefit from the French firm's long experience of the event: since the inaugural Rally Australia in 1988, its products have won eleven times. And while nothing can ever be taken for granted of course, the reactivity of the men from Clermont-Ferrand could well prove to be a decisive factor once again.

On the technical front

A reminder of the challenge. Whether they are first into Australia's celebrated 'marble'-strewn stages, or even if they are running further down the order and therefore benefit from a line swept progressively clear by those ahead of them, the drivers call for tyres that offer faultless grip, traction and steering precision over the small, round stones that act almost like a lubricant under the cars' wheels.

In reality, the ideal line is rarely swept 100% clear by passing cars. A certain amount of gravel and even 'marbles' always remain and the tyres - frequently re-cut - must slice through this layer if they are to reach the road's hard base. For it is only here that the rubber is in direct contact with the ground.

Back to winter. For a long time allocated a late-October/early- November date, the 2003 Rally Australia returns to its original September slot, that is to say the back-end of the southern hemisphere winter. At a latitude of 32° south (the equivalent of Marrakech), don't expect to see snow in Perth, but those who were around in the early days of the event between 1988 and the early 1990s (when it was organised in September) will remember that the threat of poor weather is much more likely at this time of year.

While rain has a tendency to settle the marbles and therefore minimise the importance of start order, it can also make the stages terribly slippery. In the wet, as on the dry, the optimisation of grip, traction and steering precision is consequently the key priority for Michelin's development staff.

A truly unique terrain. Since the beginning of 2003, testing outside of Europe has been banned by the regulations. Given the near impossibility of finding a terrain even remotely similar to that of Western Australia anywhere else, this new rule has not facilitated tyre firms' preparation for this trip to the other side of the equator, especially when it has come to fine-tuning their products to the latest WRC machines and most recent evolutions.

In the case of Michelin, this work has therefore concentrated on the optimisation of proven solutions thanks to the experience of the Clermont- Ferrand firm's technical staff whose record features 11 wins from a possible 15 in Perth!

Choices. Communicated to the FIA at the beginning of July, the tyre choices of Michelin's partners for Australia are based on three products: the Michelin ZE16, the Michelin Z and the Michelin ZA.

Introduced in Australia in 1999, the Michelin ZE16 swiftly established itself as an effective match for this event's unique conditions and has once again been chosen by all of Michelin's partners. Its narrow dimension helps it slice through the loose top layer while its relatively open pattern allows it to momentarily lock the small stones in its tread before jettisoning them by centrifugal force.

The Michelin ZE16 is notably likely to be the predominant option for the final leg in the Sotico forest complex (formerly known as Bunnings). Elsewhere, teams will also have the choice of either the Michelin Z (nominated by Citroën, Ford and Peugeot), which will almost invariably be re-cut, or the slightly more open-patterned Michelin ZA (Hyundai, Skoda).

Compounds. Given the increased possibility of encountering cooler conditions following the event's date switch, the proportion of '8' compound products (softer) produced by Michelin for this year's Rally Australia is higher than in recent years when the '9' compound tended to be the principal choice.

Re-cutting for enhanced clearance:

The sea-to-land ratio* of a product like the Michelin Z is around 40%. However, in order to adapt their tyres to the conditions of the moment, drivers do not hesitate to have them re-cut. The precise nature of these 'cuts' depends on individual driving styles and advice from Michelin's on- event technicians.

This work extends from a simple incision (e.g. on the inside tread blocks only) to a more complicated 'cut' (e.g. opening up of the central blocks). When the going gets muddy, Michelin's technicians may even recommend the addition of an extra circumferential groove. Between the standard pattern and this extreme example, the clearance capacity of the same tyre can be increased by more than 9%.

(*) Ratio between the surface area of the tread blocks and the grooves.

-michelin-

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