Michelin 24 hour pre-test preview

The keys to Michelin's success at Le Mans can be summed up in just three words: performance, endurance and consistency. Victory in the French long distance classic effectively demands tyres that are capable not only of running at speeds of up to...

The keys to Michelin's success at Le Mans can be summed up in just three words: performance, endurance and consistency. Victory in the French long distance classic effectively demands tyres that are capable not only of running at speeds of up to 320 kph, but equally of safely sustaining average speeds of more than 210 kph and, above all, remaining consistent for two, three and even four stints at a time. Competing in a 24-hour race also means being prepared for the unexpected, including permanently evolving track conditions and sudden changes in the weather... An ability to anticipate, react and adapt is essential. And this is where Michelin's unique savoir-faire comes into its own, a factor that works teams and privateers alike clearly appreciate, for no fewer than twenty-eight cars -- more than half the field -- will start this year's Le Mans 24 Hours on the Clermont-Ferrand firm's products.

For any tyre manufacturer, the principal challenge of competing in the Le Mans 24 Hours is the fact that opportunities to test at the circuit itself are few and far between. "Apart from the preliminary practice day, the two qualifying sessions during race-week and the race itself, the circuit is open to ordinary traffic all year round, which makes it practically impossible to test at Le Mans. This weekend's preliminary practice session is therefore extremely important," says Michelin Competition's Endurance Programme Manager, Gerard Aussage. "The track uses trunk roads that are generally very busy, so its surface is highly specific, as is the track's length, 13.6 km. To prepare for this once-a-year fixture we therefore have to turn to circuits that offer equivalent features."

This year, Michelin Competition and its partners have tested at the Italian circuit of Monza where top and average speeds are also very high. And thanks to their experience, the French firm's technicians are able to extrapolate data obtained at Monza for the development of their Le Mans range.

"Clearly," continues Gerard, "the weather at Monza at the end of November tends to be very different to what you can expect in June in the north of France, except perhaps during the hours of darkness, yet we are still able to develop new constructions and evolutions which we then validate in the warmer temperatures we get at Sebring for the opening round of the ALMS championship. For example, we already know that our 2004 tyres are more durable than last year's."

Durability -- or rather 'durable performance' to be precise -- is one of the keys to Michelin's success at Le Mans and its tyres have effectively gone unbeaten in La Sarthe since 1998. The regulations place a limit on the number of mechanics authorised to work on cars in the pit-lane at any one time. The number of nut-guns is also restricted, so tyre changes are obviously costly in terms of time. The objective is therefore to cover as many stints as possible with the same set of tyres -- without compromising either safety or performance -- and to make tyre changes coincide with driver swaps, another time-consuming operation. "In any case, drivers don't want to begin their stint with tyres that have already been on the car for one or two stints. They prefer to start their run with fresh rubber so they can manage their tyres as they see fit."

Up to four stints with the same set...

Another secret of Michelin tyres is their ability to cover two or three stints of twelve or thirteen laps each. "The performance of new tyres peaks during the first and second laps. After that, there is a slight fall-off, but then performance stabilises. At Le Mans, the fall-off of our tyres between the first and third stint is negligible. Yet we're talking about a very fast circuit, so it is highly demanding on the tyre's construction, although wear is relatively low over the smooth asphalt," underlines Gerard Aussage.

During last year's Le Mans 24 Hours, Bentley and Michelin accomplished the exploit of covering four stints in daylight, with track temperature around 25C. It was a first not only for the British team but also for Michelin "We had already succeeded in doing quadruple stints, but only during the night when temperatures were cooler. During the day, we are in fact closer to the drivers' own physical limits."

It is important to realise that four stints at Le Mans represent close to 700 km, that is to say over three hours at the wheel at an average speed of more than 210 kph! In the middle of June, inside a closed cockpit, that's a genuine test of driver stamina.

"Last year was the first time the Bentley Speed 8s competed on Michelin tyres and the challenge was to get the cars to run three stints at a time on a single set of tyres, even though the cars were entered in the LM GTP category which meant they had to run on 14" wide tyres instead of the 16" tyres used by the Audis. Bentley's engineers were sceptical at first, but we showed them at Sebring in 2003 that our products were capable of covering more than two stints, unlike the drivers! Indeed, the latter cracked before the tyres because the Speed 8 was a closed-cockpit car. The team's engineers were forced to modify the ventilation of the cockpit before Le Mans," remembers Gerard Aussage.

Qualifying tyres

Michelin takes two diametrically opposed types of tyre to Le Mans: its race tyres, developed to cover hundreds of kilometres at an average of 210 kph, and its qualifying tyres which are designed to give their best over one or at most two laps of the 13.6 km circuit. "This is a delicate technical exercise for Michelin since qualifying tyres are not employed in the other championships where drivers have to start the race with the tyres used in qualifying. Otherwise they would be forced to pit after just one lap," points out Michelin Competition's Circuit Racing Manager, Matthieu Bonardel.

Le Mans is therefore an exception inasmuch as drivers are authorised to change tyres between qualifying and the start of the race. Qualifying laps proper are generally restricted to the Wednesay evening practice session of race-week, between 8.30 and 9 p.m., or during the first fiteen minutes after the mid-session break, between 10 and 10.15 p.m. Any later, and visibility gets too poor as darkness sets in.

Michelin in fact proposes two types of qualifying tyre, one that enables drivers to put in a second flying lap should they be slowed during the first by traffic, for example, plus another product designed for a single qualifying lap, although few drivers are able to exploit its potential to the full since judicious management of the tyres is vital, a parameter that explains why it is so often experienced drivers who claim pole-position at Le Mans.

"Getting the most out of a set of qualifying tyres is an art," explains Matthieu Bonardel. "The drivers are invariably amazed by their performance for they allow them to brake 30 metres later and to corner 20 kph quicker. They can feel the tyres climb progressively to their full potential. Then, for a short period, grip is phenomenal before performance suddenly falls off, almost as though they had suffered a puncture, or driven over a patch of oil. The development of these qualifying tyres is carried out during the test sessions we organise with our partners during the year, but it's a tough challenge because there is no other circuit like Le Mans ."

But why do teams spend so much energy on trying to qualify on pole-position in a race that lasts 24 hours? Predominently for promotional reasons, since the start and the first two hours of the race are broadcast live across the planet.

Michelin's partners in 2004: Chevrolet joins the ranks of the French firm Alpine-Renault, Porsche, BMW, Peugeot, Toyota, Audi, Bentley... Many of the automobile industry's most prestigious names have placed their confidence in Michelin to help them on their way to the highest step of the podium at Le Mans.

And this year, for the very first time, Michelin will be associated with General Motors and the Chevrolet Corvette C5-Rs in their attempt to secure top honours in the LM GTS category of the celebrated endurance classic. In the 2003 race, the Corvette's bid to score a third consecutive win in the class to boost its 50th anniversary celebrations was thwarted by the Michelin-shod Ferrari 550 Maranellos which dominated the category. Yet in the American-based ALMS series, the two cars proved a pretty close match throughout 2003, with just a single point splitting them in the championship's final standings...

But while Michelin runners enjoy a certain edge round traditional circuits, their advantage becomes even more clear cut in a competition like the Le Mans 24 Hours. "We worked hard with the Chevrolet team over the winter and, at the opening round of the 2004 ALMS championship at Sebring, the Corvettes were 2 seconds a lap quicker on Michelin tyres than they were in the same race in 2003. We stayed at the circuit on the Sunday and Monday after the race to test new tyres developed specially for Le Mans," reveals Gerard Aussage.

The Audi teams have also carried out a significant amount of testing with Michelin this year. "The Audis at Le Mans this year will be private entries and the car has evolved relatively little, but our tyres have progressed both in terms of durability and performance. In general, the objective of the technical regulations is to curb the evolution of the cars.

Even so, the race distance record is repeatedly beaten at Le Mans and tyres play a major role in pushing out the overall performance envelope," says Matthieu Bonardel. "On Michelin tyres, the Corvettes are not only faster. They are above all more consistent and capable of putting in double stints with no fall off in performance."


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Series Le Mans