Q&A with Toyota’s Pascal Vasselon

Can you explain why tires have such an impact on car performance?
Tires have a huge impact on car performance simply because they are the car's only contact with the ground. To make a car quick you have to be able to generate acceleration and these forces go through the tires. You can have anything you want on the car but if the tires are not able to generate the proper friction coefficient you get nowhere. In fact, this has developed to be one of the two major performance factors in Formula 1.

How different is the challenge when we have a one manufacturer, compared to when there is a tire war?
In the recent past, when we had competition between different companies, tires become the most important performance factor, followed by aerodynamics. At the moment Bridgestone are the sole supplier so we are not developing tires any more; you just have to use them properly. I would not say it is easy but it is one step less difficult than developing them. In this situation the performance ranking changes and aerodynamics become the most important, with tire handling second. Everything is easier because the tires are consistent and you have time to learn how to handle them; you are not in a process where you have to significantly update your knowledge constantly as you are when you develop tires. With spec tires as we have now, learning the behavior of the compounds is still very important but it is easier to get on top of the situation.

What characteristics does a car need to use its tires in the best way?
You have to maintain the tires in a suitable temperature window so they can develop their grip without overheating. A tire which is too cold doesn't develop grip and a tire which is too hot will degrade too quickly and lose performance. Then you have to maintain them in their window of physical resistance so you should not overstress them to the point where the compound falls apart. So you are constantly adjusting the car set-up in order to maintain the tires in these performance windows, getting the maximum possible performance out of them.

Is tire management more challenging this season?
Tire management is more challenging this year than the previous season simply because the tires are new and we are again in a learning curve. At every race we discover more about how these compounds behave. For example, at Sepang we had the new hard specification tire, which we had no prior experience of in testing; we just had the practice sessions to learn about it. We tested with the other three compounds over the winter so we know more about them but still we have no data from races in previous seasons, as we had last year. This makes it a little bit more demanding. Also, we moved from grooved to slick tires and these don't react in the same way to graining and temperatures. Overall it is challenging but it is also very interesting.

Does the bigger difference between compounds at each race make strategy more difficult?
This year Bridgestone is bringing very different compounds in terms of stiffness and temperature range to each race. Last year, in Malaysia for example, we had the medium and hard compounds but this season we used soft and hard. This is designed to make tire management more challenging and it certainly has the potential to do that. We saw that particularly in Melbourne where we had to be very alert to tire behavior. This was particularly noticeable in Melbourne.

Why was this so noticeable in Melbourne but not in Malaysia?
The situation we had in Melbourne was that neither of the compounds was completely suitable for the track and conditions. In Melbourne we were in a situation where the super soft tire was too soft but the medium tire was too hard, so it was difficult to get the tires working in the ideal window. It was completely different at Sepang because both compounds worked in the correct window so tire management was much more straightforward.