24 Hours Centenary – The Mulsanne Straight, a stage for speed records

24 Hours Centenary – The Mulsanne Straight, a stage for speed records

24 HOURS CENTENARY – THE LE MANS EXCEPTION ⎮ The 24 Hours of Le Mans is almost as much about speed as it is endurance, with the 6-km Mulsanne Straight serving as prime terrain for competitors who dream of setting a speed record.

Circuits were often quite long in the 1920s, with Le Mans covering more than 17.252 km in its early days. These circuits usually included one or more long straights in which cars reached astonishing speeds, as well as tricky corners that reduced the average per lap. The first configuration of the 24 Hours circuit encompassed the Mulsanne Straight, the tight Mulsanne Corner, a straight that led to Arnage, then another long straight that joined at the Pontlieue hairpin (including the ultra-fast curves of Maison Blanche).

The Automobile Club de l’Ouest only began officially measuring maximum speeds in 1961. Before then, no reliable figures were recorded. But by comparing lap speed/maximum speed ratios calculated between 1961 and 1964, it can be estimated the max speed of cars in 1923 was around 120 kph. After the circuit was modified in 1932 to shorten the Mulsanne Straight and a section of the Forest Esses (then called the Tertre Rouge Esses), the best cars were topping out at around 190 kph. Just prior to the hiatus caused by World War II, Bugattis and Talbots were achieving the 200 kph mark.

First measurements

In 1953, Briggs Cunningham's team wanted a clearer understanding of exactly what happens in the Mulsanne Straight. They installed the first radar and discovered their car had reached 249 kph.

Eight years later, the ACO officially decided to measure maximum speed in the Mulsanne Straight. A radar was installed at the end of the first third of the straight, giving the cars time to accelerate fully, but well before the Mulsanne Corner where only the bravest keep the pedal to the metal.

The regulations changed significantly in 1961 with engines increased to 4 litres with 390 hp for Ferrari, from 3 litres with 300 hp the previous year. Brothers Pedro and Ricardo Rodríguez (Ferrari) passed under four minutes per lap, surpassing an average 200 kph (precisely 201.202). Ferrari's top speed measured 265 kph during the race, but Maserati was clocked at 280 kph during the free practice. Then Ferrari exceeded 300 kph during the free practice in 1963 thanks to British driver Mike Parkes.

Ford and Porsche still fastest

During the epic Ford-Ferrari duel between 1964 and 1967, top speed became a major factor with power and aerodynamics as fundamental elements. From 310 kph during the free practice in 1964 to 340 kph and even 343 kph during the race in 1967.

A new milestone was established by Porsche in 1971 with the unforgettable 917 LH (for “Lang Heck” or long tail in reference to its streamlined rear). The aerodynamic advantage was important to that model compared to short tails (917 K or "Kurz Heck" in German). The 917 LH driven by Jackie Oliver clocked an official speed of 359 kph during the free practice then 362 kph in-race, but rumours still exist today the team itself measured a top speed of 388 kph. The car benefitted from extensive wind tunnel studies at the request of Ferdinand Piëch (the head of Porsche's sporting programme at the time) who firmly believed maximum speed was essential for victory. However, a Porsche 917 K won the 24 Hours in 1970 and 1971.

The end of the Sport class (5 litres) in 1972 and the limitation to 3 litres for prototypes significantly lowered top speeds, for example 331 kph for the Lola T280 of the Bonnier Switzerland team. The following year, with long tails for Matra and Ferrari, the speed went back up to 340 kph.

But Renault-Alpine, opting for a turbocharger for its A442 prototypes, once again broke the 350 kph mark in 1976 and even 362 kph in 1978, the refined aerodynamics with a bubble on the open cockpit of the A443 having gained a few kph.

Goal: 400 kph

The 1980s ushered in new Group C regulations, with prototypes from Porsche, Lancia, Jaguar and Cougar clocking speeds between 350 kph and 360 kph in-race, and one Porsche 956 that reached 372 kph during the free practice in 1985.

In the second half of the decade, Gérard Welter and Vincent Soulignac developed long tail WM prototypes, the most successful version of which was the P88.

The Porsche 962 C and Sauber powered by Mercedes were already remarkably fast, recording 390 kph at the free practice in 1988. But, that year WM's objective was to beat the speed record. The French team waited for cooler evening temps so the V6 turbo Peugeot engine, pushed to more than 900 hp, could access more air, closing the cooling air intakes as much as possible to improve the aerodynamics of the #51 P88 driven by Roger Dorchy.

The speed record was broken at an official 405 kph, but it was said that 422 kph was also recorded on a lap, the measurement of which would have been critical. Peugeot released the 405 sedan that year, and the marque's marketing department was thrilled to be able to link a production model to the speed of a racing car!

Mulsanne from the 1990s to now

The 1989 24 Hours was the final race where the Mulsanne Straight existed in one uninterrupted section. In 1990, it was divided in three by the two chicanes we known today. Before this major change, Sauber Mercedes clocked 400 kph in practice and the Jaguar XJR9 389 kph in-race.

The addition of the chicanes obviously decreased top speeds in the Mulsanne Straight. The length of each section is too short to go after more kph and  the chicanes require more downforce to achieve a good lap average. The glory days of 3.5-litre atmospheric engines at the beginning of the 1990s nevertheless facilitated speeds of 346 kph in-race for the Peugeot 905 in 1993.

Since then, speeds in the Mulsanne Straight have varied between 320 kph and 340 kph, and thanks to the chicanes, the official 405 kph clocked in 1988 may remain a permanent record at Le Mans.


PHOTOS (Copyright - ACO Archives): LE MANS (SARTHE, FRANCE), CIRCUIT DES 24 HEURES, 1953-1988 24 HOURS OF LE MANS. From top to bottom: after night fell at the 1988 24 Hours, the WM-Peugeot P88 set its sights on a speed record; in 1953, the Briggs Cunningham team executed first measurements of maximum speed (pictured here the car of John Fitch/Phil Walters, third in the race that year); between 1964 and 1971, speeds reached staggering levels thanks to Ford (here the victorious 1967 Mk IV) then Porsche; on the WM P88 that Roger Dorchy shared in 1988 with Swiss driver Claude Haldi the streamlined rear wheel arches for speed.

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