Pirelli explains tyre behaviour at 350km/h

At last weekend’s Italian Grand Prix in Monza, Red Bull driver Daniel Ricciardo – the winner of three grands prix this year – reached 362.1 kph (while slipstreaming) on the main straight: the highest top speed that will be clocked in 2014.

At the speed Ricciardo recorded, the wheel is rotating around 2800 times every minute, or just under 50 times every second.

These extreme speeds have a profound effect on the tyres. At full speed, which is frequently the case during a lap of Monza, a Formula One tyre is often subjected to a downforce load up to 1000 kilograms. Another important aspect is that the high speeds generate a huge centrifugal force on the tyre itself.

Because of these loads, the footprint of the tyre increases and the part of the tyre against the ground is subject to a lot of deformation, as shown in illustration 1 below. The structure of the tyre has to be incredibly strong and elastic to cope with this constant flexing.

In red: beyond 350kph, the part of the tyre in contact with the asphalt undergoes notable deformations.

At the same time, the upper section of the tyre (which is not in contact with the ground – illustration 2) is subjected to a big centrifugal force, but despite this the shape of the tyre does not change much: stretching by just 1%. This is due to the low weight and extremely high stiffness of the materials developed by Pirelli for Formula One.

Beyond 350kph, the highest part of the tyre only changes shape by 1%, despite being subject to an enormous centrifugal force.

The F1 tyres are designed precisely with these extreme forces in mind: during laboratory testing, before they even see a race track, the tyres are exposed to higher loads and forces than they would normally experience, and accelerated to speeds of up to 450kph. Not only that, but they are also fired into solid surfaces at speeds in excess of 250kph: simulating the impacts with kerbs for which Monza is also famed.