24h Le Mans
24 HOURS CENTENARY – PERPETUAL INNOVATION ⎮ In its 100-year history, innovation in cars and circuit infrastructure have been a top priority at the 24 Hours of Le Mans. For example, special attention has always been paid to the quality of the track's surface, which greatly influenced the modernisation of the French road network during the first years of the race.
With the 1906 Automobile Club of France Grand Prix fast approaching, Le Mans regional officials began concerning themselves with repaving area roads. As a result, 103 km of national, departmental and private roads underwent tarring tests. Despite good intentions, on the day of the Grand Prix the ambient temperature of 36°C in the shade caused the tar to melt. As the cars were not equipped with mudflaps, tar was kicked up into drivers' faces when overtakings were executed. The event's lead doctor, Professor Rothschild, treated many cases of what was called the "ophthalmia of Le Mans."
Ahead of the 1921 24 Hours of Le Mans Endurance Grand Prix, the indefatigable ACO Secretary General, Georges Durand, insisted road surfacing be a major priority. The circuit therefore became a veritable test laboratory, reloaded with porphyry (rock consisting of coarse-grained crystals) from Voutré. To this day, the quarry in northwestern France still supplies quality materials for roadway sub-layers and railway ballasts.
In 1922, and again in 1923, new tarrings were carried out, but very few repairs. Unfortunately, terrible weather conditions at the inaugural 24 Hours of Le Mans damaged the integrity of the track and, after just a few hours, pepples uncovered by the downpour began to "fly low" and cause significant damage to the cars: many headlights and windshields were cracked, and radiators and tanks perforated.
For the 1924 running of the race, the coating was restored by adding a third layer of tar, tar-bitumen and gravel. Meanwhile, Durand continued to call into question the government, which was spending a fortune building roads made of concrete and cement. Though heavy traffic at Mulsanne (on the route from England to Spain) was clearly having little effect on the road surface, it was no easy task for the ACO Secretary General and local engineers to convince the State to opt for less expensive methods.
The rest of the circuit, not subject to traffic, was treated differently by the use of silicating (a concrete sub-layer covered with a mat of hydrocarbon products) and vialitage (the incorporation of a tar-bitumen emulsion in cylindrical materials and a surface finish with a gravelled mat). Thanks to these different processes, the 24 Hours circuit has been able over the years to maintain its position as a testing ground for technologies related to the development and modernisation of road networks.
In 1926, 1927 and 1928, the ACO organised a Road Tournament at the circuit (three sections of the Mulsanne Straight had different surfaces) allowing 10 competing companies (including one Swedish) to demonstrate the merits of their road surfacing products. In 1927, Road Day hosted 300 guests at the circuit: representatives of ministries, automobile clubs and even chambers of commerce, deputies, senators, prefects, engineers and mayors attended bithulite spreading demonstrations during the event. At first reluctant to adopt the techniques recommended by the ACO, the Minister of Transport at the time, André Tardieu, was finally convinced. The day was an undeniable triumph, and the savings achieved at the national level thanks to the adoption of Le Mans techniques made it possible to restore the French road network in four years, instead of the 40 that would have been required by the government's methods.
The seal coating is currently repaired every five to six years with extreme focus paid to the choice of grain size. Laser surfacing makes it possible to vary the track's profile crosswise at various points on the circuit, going from a "roof" profile at Mulsanne to profiles with a negative slope (karting corner) or positive (Indianapolis curve) to facilitate rainwater runoff.
PHOTOS (Copyright - ACO Archives): LE MANS (SARTHE, FRANCE), CIRCUIT DES 24 HEURES, 24 HOURS OF LE MANS. At top and centre: after the 1927 24 Hours, the French government decided to adopt the ACO's track resurfacing methods for the renovation of the country's entire road network. Above: the markings on the ground seen in this photo show another unique aspect of the circuit, wherein a major portion borrows roads open to public traffic the rest of the year.
