When the going gets rough - tyres and track surfaces 24 Jul 2008
Formula One tyre suppliers Bridgestone have a very big part to play in how much grip drivers have at their disposal in a Grand Prix, but there is one aspect where grip is out of Bridgestones hands, and that relates to the track surface.
During the course of this season, Formula One visits 18 tracks, each of which has its own distinctive surface. From the public roads of Monaco, to the dedicated motorsport surfaces of the permanent circuits, each has its trademark fingerprint.
There are many different surfaces encountered at race tracks around the world, says Bridgestone Motorsports Director of Motorsport Tyre Development, Hirohide Hamashima. For example, public roads which are also used as race tracks have different design considerations from tracks which are dedicated motorsport facilities.
The circuits that Bridgestone visit vary in many ways, and the make-up of the track surface can be very different.
Track surfaces are predominantly asphalt, although we do see concrete at some motorsport venues around the world, says Hamashima.
Two main track factors determine the allocation of tyre compound for a circuit: the layout and the roughness of the track surface.
Layouts obviously vary a lot and the differences can easily be seen. says Hamashima. However, there is a big difference between the extremes of the smoother surface circuits we visit, such as Monaco and Montreal, and the more abrasive circuits such as Silverstone and Barcelona.
Track surface is not a constant, and over the years, the track can change as it ages.
As a track gets older, different things happen, explains Hamashima. For example, the colour of tarmac can often fade, so a new track is more black than an older surface, and the darker surface attracts heat from the sun more than a lighter surface.
If a track is used frequently, the surface becomes smoother, but also the bitumen gets worn away bringing the stones to the surface so it can be difficult to predict exactly how we will find the surface when we visit a circuit.
Bridgestones tyre engineers scan the track surface at a number of points early in the race weekend so they can analyse the surface, and see how it has changed from previous seasons.
Over the course of a race weekend the track surface changes as rubber goes down. Early in a Grand Prix weekend a track surface usually has less grip than it will have after Formula One cars have been running on it. We call the track surface green before it has rubbered-in, explains Hamashima.
Some tracks get a lot of motorsport use and the change over a race weekend with these circuits is less extreme than at a track which is seldom used. When the track does not get a lot of use we see a more dramatic change of grip level provided by the track over the race weekend.
Of course, tracks do get resurfaced, and some more than others.
When a track is resurfaced there are a number of issues, says Hamashima. If the track has been resurfaced in its entirety, we have to analyse the new surface and sometimes this means a change in our thinking when approaching that circuit.
A freshly laid track often still has oils coming out of it, which presents a slippery surface when it is initially used, especially if it rains.
Tracks are not always resurfaced in their entirety however. We often see circuits which have certain parts resurfaced, the most extreme example of this being the Montreal track recently, where track problems meant the hairpin was resurfaced after qualifying on Saturday, before Sundays race, says Hamashima. We do not see this often.
Unless the different types of track surface differ dramatically, two or more surfaces over the course of a lap do not present a big challenge for Bridgestones tyres, but for the drivers the opposite can be true.
Where there are different surfaces over the course of a lap, a driver has to be very vigilant as the grip levels will vary, and this can make for an interesting time behind the wheel, says Hamashima.
Another area related to track surface is when the heavens open and rain falls. In the wet there are a number of different track surface considerations, says Hamashima. Some surfaces give more grip than others when they are wet, and the amount of water drainage a surface allows has a big influence on which tyre can be used, and how well that tyre performs.