Why does Formula E have 18-inch, treaded tyres?

One of the most frequently asked questions about Formula E is why the series runs on treaded tyres rather than traditional racing slicks.

To answer that, and to explain the whole philosophy behind the design and construction of the tyres, Formula E visited Michelin Motorsport in Clermont-Ferrand where Pascal Couasnon, director of Michelin Motorsport, Serge Grisin, Formula E Project Manager at Michelin Motorsport and Estelle Perrier, the development engineer who designed the Formula E tyres gave us the inside line.

Why is the tyre treaded?

Grisin: “We proposed to have a patterned tyre to reduce the number of tyres developed, produced and transported to races. A rain tyre is something you bring a lot of time to tracks and you bring back a lot of time without running it.”

Couasnon: “I understand that we are under some extreme conditions sometimes you have to have very specialised tyres but in this case we wanted to meet a challenge and get closer to reality – you don’t change your tyre when it goes from dry to wet, well let’s try to do the same thing in racing – so far we haven’t had rain, but we know that the tyre works very well in the wet, and the feedback has been extremely positive.”

Perrier: “To be able to decrease the number of tyres you have to have a polyvalent approach. A tyre able to operate in slick and wet conditions. To be able to operate in wet conditions, even with a small quantity of water you need to have a groove. We adapted the compound and the groove to find the best solution with the best level of performance in each area. Another illustration of the good tyre polyvalence is its ability to operate in a wide temperature window. We have performed some tests in wet conditions at 5C with no problem of warm up and in slick conditions at 54°C with no problem of degradation.”

Why is it 18 inch?

Couasnon: “The idea of the 18-inch tyre is something that we had in mind for quite some time. As a matter of fact as early as 2010 we were proposing to the FIA and Formula 1 to evaluate it and really bring the racing tyre closer to the street. I was looking at the cars on the street this morning and I don’t see small wheels and big sidewalls. I’m not saying the tyre on the track is exactly the same but the physical principles are the same.”

Grisin: “Our technical proposal was to find items that have better technical efficiency. Not only rolling resistance – and 18-inch is good for rolling resistance because you have good deflection. A big part of the rolling resistance is coming from the deflection of the sidewalls. It was a good idea to make a very easy link between a road tyre and a racing tyre because 18-inch is a very common size now in sportscars.”

Perrier: “With an 18-inch tyre you are able to have a longer area of contact and less deformation so less energy is needed to deform on the ground.”

How was the tyre developed?

Grisin: “We were informed that we had been selected as the exclusive tyre supplier in the end of March 2013 and the Frankfurt Motorshow in beginning of September was the first time the car was being seen in the public, so there was no question for us – we needed to have the pattern tyres ready for that event. So that meant in five months we had to get information from the car: create and design the tyre, create the moulds and produce the first tyre. It was really tight but we managed that.”

Perrier: “We have designed this tyre to be a competition tyre and we were waiting for this project to evaluate new technology. The idea is to find technology thanks to competition and to bring this technology for all the consumers because electrical vehicles will be much more present over the next five or 10 years.”

What lessons have/will be learned for road tyres?

Couasnon: “We have already learned a few things in terms of grip – we have been on very different surfaces and the feedback from the drivers has been unanimous. I was talking in Miami with Jean-Eric Vergne and he was saying there is absolutely no issue, it’s almost a simulator tyre, which is very consistent and you can really attack. You have to manage your energy, you don’t have to manage the tyres, which is the goal. This means that the compound we are using will be able to be transferred to the street. The other thing is that we have some very fundamental projects with our technology centre to understand even further the role of tyres in terms of energy consumption of the car. We are at the beginning of the programme, but the data that we are acquiring is already starting to feed this major project. I know that what we’ll learn will be very useful for the future.”

Perrier: “We want to progress on the topics of energy efficiency in performing some analytical tests and modelling in order to be able to show the benefit of one tyre compared to another. We are in an innovation area. It’s not only innovation in terms of technology, it’s innovation in terms of simulation tools, in terms of methodology and even in terms of test methods. I think it’s only the beginning, we have lots of things to learn, lots of areas to identify. Our ambition is to find some new technologies and to transmit this technology to our car tyre product line.”

How does the tyre work in the wet?

Grisin: “They are street races, so that means lower speed and there is no tyre warming systems allowed. All these things pushed to design a cold compound tyre. Our target every day is to develop tyres with more performance in all the different areas. We tested in the wet at Donington on several occasions, and at Issoire with artificial rain and we are really confident with the performance of the tyre in the rain. But clearly we haven’t had the chance to experience it in the race, so we’ll have to see.”

How has the tyre performed in the seven races so far?

Perrier: “We are very happy with the behaviour of the tyre. We have good performance in terms of warm up, in terms of grip, consistency, no problems in terms of damage, so good endurance. We have a very small amount of wear, which is a very good point and opens opportunities. For the first year in a context of many open questions we wanted to provide a very robust solution in order to make all the drivers happy with the tyre. As you have seen in the first race even on contact with the wall there was no problem with the tyre – it was very strong. For Michelin safety is the main point.”

How is Michelin involved with Formula E’s legacy programme?

Grisin: “We have an internal sustainability programme. Everything regarding sustainable mobility is one of the key targets for Michelin, so being involved in the legacy programme was a no brainer. The idea of leaving the bib inflators [in host cities] was to help the road safety and the carbon footprint. Having the right pressure has two impacts: improved safety because if you have the wrong pressure it can cause unusual car behaviour and efficiency because if don’t have enough pressure you will have a bigger rolling resistance and you will have higher fuel consumption. Having bib inflators will allow the public to check the pressure, to adjust the pressure and to have better safety and energy efficiency.”

How will the tyres develop in the future?

Couasnon: “The Michelin Total Performance philosophy is always how do you continue to improve all the different performances without degrading one? We are used to thinking of a tyre as a compromise – if you improve something you lose performance elsewhere – and this is not the philosophy of Michelin. It’s through innovation that you break the compromise. We want to continue to increase what’s important for you and me, which is safety, efficiency and longevity. One thing we are looking at with the FIA and Formula E is how can we double the racing life of the tyre and that’s something that could come as soon as next season. The rolling resistance is one characteristic that is a measure of the energy-efficiency of the tyre, we’re going to try to have something where we keep the grip or even increase the grip and improve energy efficiency. So that’s the programme. Potentially lower the mass of the tyre, because if you transport less mass you are more efficient. Also by doubling the racing life of the tyre, you consume fewer raw materials. It’s a very ambitious goal but we believe that we can reach it.”