At each MotoGP race, Michelin offers riders three types of tires at the front and two at the rear, drawing from a range of around thirty different specifications. This selection owes nothing to chance and follows a long process of simulations, carried out on a computer and in a dedicated machine, particularly when new circuits join the championship.
Ahead of the launch of the 2024 season, Michelin opened its doors to a selection of media, including Motorsport.com, to explain its working methods. Taking the example of the Indian GP, which joined the calendar Last season, Romain Cacheux, in charge of designing the tires used in MotoGP, explained the procedures put in place to determine the more or less soft rubbers to bring to Buddh, where no testing could be carried out before the race.
“From the moment we have no data and no possibility of doing tests, we use simulation a lot”underlines the engineer. “This will mainly be the operating points of the tire, in terms of load, effort, speed, camber, temperature… We need to understand how the tire will perform on this track, to choose the right tire. carcass and carefully choose the mounting materials on the tread.”
This process requires several weeks as the parameters are so important. By using models integrating the motorcycle, the rider and the tire, Michelin simulates a lap and thus has an initial idea of the times, which makes it possible to anticipate the stresses on the tire. To do this, you must not simply enter the route data but get as close as possible to the trajectory taken by the pilots… and the engineers sometimes base themselves on completely public data.
“Either we have [les données des trajectoires] because we know the circuit, we have already done tests, whether in WorldSBK, or with our bike [de tests]and we recover the trajectory in the data that we know”specifies Cacheux. “Either, in the case of Buddh for example, we have no information and we simply use Google Maps. We retrieve the map, we trace a motorcycle trajectory on the map and it is this trajectory that we come to enter our simulation tool.”
Romain Cacheux, tire designer for Michelin
The simulations therefore start from a “generic tire model”always with the same architecture and the same model, and analyze what the link will be between the tire and the motorcycle over the entire circuit. “Even though we are a tire specialist, we also do a lot of vehicle dynamics, as the teams can do”underlines Cacheux. “We don’t do it at the level they do it, we don’t need the level of precision that the teams have to get the last thousandths or hundredths of a second.”
“What we want is to have the right load transfers, the right cambers, the right camber speeds to apply forces to the tire that are relevant to what is actually happening on the track. “
What we want is to have the right load transfers, the right cambers, the right camber speeds.
Michelin thus determines the average passing speeds, the maximum loads on the front when braking, the degrees of camber, the energy absorbed by the rear tire or even the asymmetry caused by the circuit in all these constraints.
New software is then used to analyze tire-related needs more specifically, by simulating deformation and temperature changes over an entire lap. The goal is to determine a thermal severity, in particular if it is more or less symmetrical, and a mechanical severity, to rule out any endurance problems.
Michelin can then begin to think about the best tires for the circuit, but for this, the manufacturer does not look at the characteristics of each rubber in its catalog, and rather prefers to classify the track in relation to the others. This makes it possible to compare the circuit to the already known base, thanks to existing data on other events, by retaining the criteria of temperatures, asymmetry and mechanical severity, and to relate to the selections made for these races.
In the case of Buddh, it was especially the center of the tire which was highly stressed thermally, but the mechanical stresses were low. “At this stage, we say to ourselves: ‘I think that with this type of architecture and this type of mix, we can get by’”underlines Cacheux. “The tires, we have them, in general, we take tires from the range. If we don’t have them, we make specific tires – there are some tracks where we have specific tires. Once that we have the tire, we move on to the measurement part.”
The Record machine, the test bench that reproduces a circuit
Michelin has a spectacular tool for simulating any circuit, the Record machine, visible in the video below and located on the Ladoux campus, the manufacturer’s gigantic research and development center, which covers 68,000m².
In a dedicated room, we find a huge cylinder, three meters in diameter and with a strip of asphalt inside, and this wheel rotates at very high speed, reaching up to 350 km/h. A mechanical arm “places” the tire inside this cylinder and simulates the track, reproducing the camber angles, up to 60°, while the rotation speed of the machine adjusts to align on that of the circuit studied.
“We go on the machine to validate performance and endurance”notes Romain Cacheux. “It’s still first and foremost endurance: we make sure that the tire lasts the distance of the Grand Prix, […] with no damage, correct performance, etc.”
VIDEO – The Record machine, Michelin’s test bench
It is possible to simulate several types of floor, relying on materials similar to sheets of glass that are used for sanding, but Michelin carries out this work without precise data on the grain size of the circuit that will be visited. Surface analyzes are very complex and no actor, whether the tracks, the FIM or Dorna, is able to provide sufficiently detailed data to Michelin, which makes its own measurements once on site. place. The need for extreme accuracy in this data is not present anyway.
“It’s a big factor, which certainly affects the level of grip on the track, but above all the wear at the end. We have models, we are able to model surfaces, we are able to quantify the effects of a ground on the level of tire grip and on tire wear. On the other hand, we do not need to go down to this level of precision to anticipate a soft-medium-hard range over a weekend. end of Grand Prix.”
“If you really want to do ultra haute couture, be sure to have the ‘best grip ever’, if you were fighting with a competitor for example, […] we would do this kind of analysis, and we would do them [face à Bridgestone par le passé, ndlr]. Today, what we are trying to do is to have approximately the same performance as elsewhere, to be locked in endurance – to be sure that there will be no problems with endurance – and that this is rideable for everyone in good conditions. And that’s what happened [à Buddh].”
Track checks
Once on the circuit, temperature measurements are taken and comparisons are once again made against other circuits, to ensure that the choice of tires was wise. Wear measurements are also taken from the first sessions and allow us to see the cumulative energy on the tour, and in particular the most problematic areas.
At Buddh, the most demanding section was from the exit of turn 3 to the entry of turn 4, the longest straight on the circuit, from go-around to braking, with very pronounced wear and an uphill climb. in unusual temperature.
“With this data, we went to see the teams, showing them these results, to tell them to pay attention to this area and either work on the settings of the bike, or ask the rider to manage the throttle in order to preserve the tires on this area, since it was the critical area identified for the tire”explains Célia Gordon, performance analyst engineer at Michelin.
A Michelin tire during its manufacture
“Out of the total energy spent on the tour, this area corresponds to a quarter of the total energy spent”she added. “We are taking a big step in energy, which is not negligible at this location.”
The teams having been able to manage the situation without losing too much performance, tires equivalent to those selected for 2023 will again be chosen for Buddh this year. The simulations therefore played their role.
Several steps for a new range of tires
Michelin must restart a whole part of this process for the development of the new front tire which must be launched in competition in 2025, and whose aim is to better respond to the constraints posed by aerodynamics, in particular by using stickier compounds and a new construction. Before embarking on the manufacture of prototype tires, simulations were carried out based on different concepts and several stages made it possible to reduce the selection tested on the track to a few examples.
“In our classic development process, when we decide to release a new tire, we generally start with simulation”details Cacheux. “Not quite the same kind [que pour un nouveau circuit]more [on débute] through simulation. For example, we have around ten tire solutions, which we validate in terms of performance and endurance on [la machine Record].”
“Out of these ten choices, we only keep three or four, because we eliminate problems of endurance, performance, etc. And on these three or four tires that we think are interesting, we pass on note test bike, we are going to ride with our test riders on the circuits [du MotoGP]. We drive a lot in Spain, in Italy, wherever we need to go. We are going to validate performance and endurance on our Superbike.”
For these tests, currently led by Sylvain Guintoli, Michelin is using a Honda Fireblade modified to integrate an HRC kit, a WorldSBK fork and MotoGP brakes. It is equipped with a battery of internal and external infrared, pressure and even temperature sensors to analyze all movements and variations on the tire.
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