Le Mans 24: Braking performance versus F1
Despite their similarities and incessant chase to faster lap times, the difference between braking systems in both series is quite large. In Formula 1, there is a lot of intense deceleration where the values often surpass 5G (at Monza it gets up to 6.7 G), but at the 24 Hours of Le Mans, the braking force does not go over 3.5 G.
The reason for this wide gap is the difference in mass of the two prototypes. A Formula 1 single-seater has a minimum weight of 733kg including the driver while an LMP1 car racing at Le Mans weighs at least 875kg plus 3kg for camera gear or a spare power pack. Of course, non-hybrid LMP1 cars can weigh up to 45 kg less, which means the overall weight drops to 833kg.
The main difference are of course due to the differing lengths of the races, with max 120 minutes in F1 to 24 hours at Le Mans. This makes that the only common factor these cars share is that their discs are made of carbon. What is different, and by a lot, are the disc properties, as outlined below:
|Property||Formula 1||24 Hours of Le Mans|
|Disc thickness||up to 32 mm||30-32 mm|
|Front disc diameter||278 mm||up to 380 mm|
|Rear disc diameter||260 - 272 mm||up to 355 mm|
|Number of ventilation holes||Over 1400||Between 36 and 430|
|Range of use||662-1832°F||662-1472°F|
|Wear per event||less than 1 mm||3-4 mm per disc and 8-10 mm per pad|
The difference in the disc diameter is linked to the size of the rims used in the respective championship races. Currently in Formula 1, 13" rims are allowed. At the 24 Hours of Le Mans the cars are equipped with 18" rims.
Two extremes in ventilation
In Formula 1, ventilation is crucial to preventing the system from overheating. Depending on the forecasted air temperatures during the Grand Prix and the specific race strategy, each driver chooses from three different Brembo disc solutions: Around 900, 1,200 or 1,400 holes.
The teams rely on personalized cooling schemes, an element that is essential for improving heat dissipation. The temperature of the F1 discs can get up as high as 1,832°F during the race. Ventilation of the LMP1 cars is not as intense at the 24 Hours of Le Mans because the teams actually have the opposite problem: Rather than cool down the systems, they have to keep the temperature from dropping too low, especially at night or during neutralization phases.
That explains why these cars use the same number of ventilation holes that the Formula 1 cars used years ago. At Le Mans, it is important to keep the carbon discs from dropping below 662°F, which would cause the friction material to glaze, reducing braking efficiency and resulting in premature disc wear.
To prevent this from happening, friction material for discs and pads are on offer with more efficient thermal conductivity.
Different wear, integrated checks
Just like in Formula 1, the LMP1 cars racing in the 24 Hours of Le Mans use Brembo carbon brake pads. Naturally, the pads they use are thicker to guarantee they remain fully operational for the entire 24 hours.
Just consider that pad and disc wear during a Formula 1 race is less than one millimeter, while the prototypes racing in Le Mans consume 3-4 mm per disc and 8-10 mm per pad.
To monitor consumption, the Formula 1 single-seaters are equipped with sensors that continuously relay the temperature of the discs and calipers to the engineers in the pits. In some cases, the sensors also monitor the status of the pistons so that they can calculate disc and pad wear.
Monitoring these elements enables proactive problem-solving in different conditions of use and communication with the driver in real time about modifying brake balance and recovering energy from braking the single-seater.
In addition to sensors, the Brembo discs on the prototypes at Le Mans have slots with a range of depths that make it easy to quickly check the status of the discs when the car is in the pits for refueling or to change the driver. When one of these slots is no longer visible, it means the disc has been consumed more than the depth of the slot when new.
Obviously, when the last slot disappears, the disc has to be replaced because the level of performance has gone down.
Braking performance compared
It may seem impossible to compare the braking performance of these two types of cars since they don't race on the same track.
To get around this problem, a comparison was made between the hardest braking done in the two competitions, calculating the average deceleration of each as it relates to braking time and distance. In general, the Formula 1 and LMP1 cars are very different and their behavior during braking can't and shouldn't be attributed to the brakes alone.
The race cars have different weight distributions and aerodynamic loads, but even more importantly their tires differ in size and compound, which plays a significant role in braking performance. Although not perfect, this comparison still provided interesting results.
On Chicane 1 at Le Mans (turn 5 on the track), the LMP1s arrive going 208 mph and they brake for 3.21 seconds during which they travel 195 m. The cars enter the corner at 68mph thanks to the driver applying a load of 220 lb on the brake pedal. Deceleration during braking hereby peaks at 3.5 G.
In comparison, F1 cars entering Parabolica at Monza (the last turn on the Italian GP track) brake from 314 km/h to 204 km/h in just 1.22 seconds, on a stretch of track that only measures 72 m. The drivers are required to apply a remarkable amount of force: 6.7 G in deceleration and a load of just over 200 kg on the brake pedal.
That means a Formula 1 race car is able to drop more than 88 km/h [314-204 km/h)/1.22] in one second, while the top-end LMP1 cars can only reduce their speeds by 69 km/h [(334-110 km/h)/3.21] per second.
The numbers of braking performance in F1 are confirmed also when looking at high downforce tracks like Singapore and Monaco. On Turn 1 of the Marina Bay Street Circuit in Singapore, the Formula 1 single-seaters brake for 1.98 seconds to go from 294 km/h to 135 km/h: That means in one second they drop more than 80 km/h. And on the first corner after the tunnel (Turn 10) at the Monaco GP, the single-seaters go from 286 km/h to 93 km/h in 2.03 seconds: In essence, in one second they decelerate 95 km/h.
The difference may seem minimal, but said another way it really is impressive: In 72 m of braking, the Formula 1 single-seaters go down more than 105 km/h, while in the same amount of space the LMP1 prototypes decrease their speeds by about 69 km/h.
In short, Formula One cars display superior braking performance to LMP1 cars, thanks to a varying number of factors. But then again, they'd all end up with worn brakes after just 1/8th of the distance of the 24 hours challenge that is Le Mans.