Tyre talk with Michelin and Williams

Of all the components that make up an F1 car, tyres would seem to have the most resemblance to those used on an average road car, but appearances are deceptive. While the general concepts of what a tyre is and what it is supposed to do are the...

Of all the components that make up an F1 car, tyres would seem to have the most resemblance to those used on an average road car, but appearances are deceptive.

While the general concepts of what a tyre is and what it is supposed to do are the same regardless of the application, the operating conditions and goals of motorsport dictate a dramatically different outlook toward design and construction. Looking at durability alone, while the average road car tyre is designed to have a lifetime of thousands of kilometres, an F1 tyre is built to deliver maximum performance for around 200km. With that kind of use, and in order to support all their teams with the right tyres on race day, Michelin will bring over 2000 individual tyres to every Grands Prix.

Here we talk about the tyre technology in F1 with Pascal Vasselon, Michelin's F1 Programme Manager. Pascal is in charge of 19 engineers at each GP (three for each team), and has spent most of his career in Motorsport, including several Le Mans-24hr events and touring car championships.

Q: How does the BMW WilliamsF1 Team tend to use the allocated ten sets of tyres over a race weekend?

"Usually we use three sets on Friday, simply because we have to give three sets back to the FIA in the evening, so the best practice is to use them. Then, depending on the race strategy we intend to have, we use between one and three sets on Saturday morning, and usually four sets in qualifying. During the race, again depending on the race strategy, we will use scrubbed tyres or the rest of the new tyres."

Q: Is there a special set-up for qualifying?

"Yes. After Saturday morning testing we tune the pressures and temperatures to optimise performance for the qualifying session. In terms of tyre pressure we usually use a lower pressure for qualifying, but during the season, from track to track, there is usually not that much variation."

Q: Why do Formula 1 dry tyres often require some time on the track before reaching their optimum performance?

"This is a characteristic of grooved tyres. When the tyres are new there is sometimes too much movement in the grooves so we sometimes scrub the tyres to help stabilise this movement."

Q: Does driver style influence tyre design or selection?

"Sometimes we see some differences in the wear rates and the balance, and that leads to adapting tyre fittings to each driver in terms of pressure, balance of pressure, and sometimes a number of laps for scrubbing the tyres. In some cases, even the direct tyre choice or compound can be different."

Q: How do you use telemetry information from the car to improve the design of tyres?

"It's the first data we look at even before we go to a race track. The most important parameters we look at are the vertical loads on the tyres and the speed. With these two parameters we want to be sure first of all that our tyres are able to support the car at the top speeds with the loads that correspond to this top speed. This is the first development step, and then we look at the range of speeds and accelerations."

"The lateral and longitudinal acceleration of the tyre are directly influenced by the grip of the tyre. So we have a precise analysis of this data and for the balance of the car we look at the steering wheel angle. I would say that loads, speed, accelerations, and steering wheel angle are the data we are always looking at. In some cases when we are chasing a particular problem, we may look in more detail at other parameters such as wheel displacement or differential slip."

Q: What are the major factors involved in selecting tyres to bring to a circuit, especially to a track that you can't test at?

"There are three different parameters. Firstly, track layout in terms of the number and length of corners and the length of straights - that sets a requirement for tyre reliability. The second set of parameters we look at before coming to a race track are the characteristics of the actual surface. The last parameter is the weather forecast....the most likely conditions we can expect to encounter over the weekend."

Q: Is a smooth track surface usually better on tyre wear?

"It depends. If you have grip then you have less wear on this type of track, but if your grip is not sufficient you can slide, and as soon as you slide you have a lot of wear, so the answer is never known in advance. A smooth track can be very aggressive on tyres as soon as you loose grip and have a lot of sliding. A long sweeping curve is also more demanding, rather than a chicane."

Q: Does track temperature primarily determine the choice of a softer over a harder compound?

"Track temperature is just one parameter we have to take into account. Other parameters are also important for the decision. If you have a car that is not demanding on tyres or a driver which doesn't push too much on tyres you can use a softer compound when it there are extremely hot ground temperature."

Q: Do you do any work on the aerodynamic effects of the rotating tyre?

"Yes, we know that it is important, so we try to take into account aerodynamic requirements, but its so important to make a tyre compound to work well that on many occasions something that is a loss in aerodynamics is a big gain on the race track, so ultimately we look at the lap time! So we do take into account aerodynamic requirements but it is not the first priority. It is similar with loads. We know that we must save the mass of the tyre but on many occasions a heavier tyre has been a quicker tyre so in the end we of course try to do it as light as possible but if adding some weight somewhere improves the lap time in the end we will take it!"

Q: What computer simulations and modeling do you use, and have Michelin developed these in-house?

"We do a lot of modeling work at Michelin using the finite element method. The Formula 1 tyre is so specific in terms of working in the most difficult physical processes compared to a road tyre that we cannot buy commercially available software. We are working with very large displacements, with fully non-linear viscous-elastic materials, so the finite element model is very complex."

Q: What are your thoughts of the use of computers in sport and the future?

"We cannot live without them! Everybody now has databases of information on PCs and all our people are connected to the network of our company, so at the moment we could not work without this ability to share information. We are away from our offices 50% of the time so without computers and the associated networks we could not be efficient, so it really is part of our life now. In any sport where technology is important for the final outcome such as sailing or motorsport, computers are central to winning."

Q: Is there much technology, processes, techniques, etc you can transfer between other Motorsports and F1?

"Yes and no. Yes in that from Rally and MotoGP we know how to handle racing activities and logistics, how to handle tyre production, and how to handle development. However, in terms of design, F1 tyres are completely different so we don't optimise the same performance criteria even though in the beginning the modeling technology is the same. For example, the life of the tyre is completely different. And, an F1 tyre has more lateral movement than a GT or super touring tyre because of the greater length in the sidewall."

Q: Do you think tyre development and technology will change dramatically in the future or will it be a slow evolution from race to race, season to season?

"We have continuous improvements just to have products which are better suited for each race track, and we have sometimes, of course, changes in the compounds or casings that are developed in the factory and arrive to test. So, on the one hand we have continuous adaptation to the race track that is a continuous process, and at the same time we have new in-house developments of materials, profiles and manufacturing."

-williams-

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Series Formula 1
Teams Williams