Formula One is poised for one of its most highly-charged weekends of the season, as local favourite Fernando Alonso (Mild Seven Renault/Michelin) bids to extend his world championship lead on home soil at the Circuit de Catalunya. Unbeaten for the past three races, Alonso is aiming to become the first Spaniard to win his home grand prix.

So far this year, six Michelin drivers from five of the company’s seven partner teams have shared 10 of a possible 12 podium finishes – and Alonso has yet to finish outside the top three. Race tickets sold out well in advance and a capacity crowd of about 125,000 is expected on Sunday.

This weekend’s event will be the 35th Spanish Grand Prix to count towards the F1 world championship. The country first appeared on the calendar in 1951, with a street race in Pedralbes, Barcelona that was repeated in 1954. The race has since been staged at Jarama (nine races, between 1968 and 1981), Montjuich Park (also in Barcelona – four, 1969-1975) and Jerez (five, 1986-1990) before it moved to its present home in 1991. This will be the 15th F1 race at the Circuit de Catalunya.

Jarno Trulli was the best-placed Michelin runner in last year’s corresponding fixture, when he took his Renault to third place, fractionally ahead of team-mate Alonso.

This weekend the company is seeking its 80th F1 world championship success – but only its second in Spain.

The first was one of the most memorable in F1 history, however: in 1981, Gilles Villeneuve (Ferrari/Michelin) fended off fierce pressure. Villeneuve beat Jacques Laffite (Ligier/Michelin) by 0.211s – 0.004s tighter than Fernando Alonso’s winning margin in the recent San Marino GP.

Pierre Dupasquier, Michelin motorsport director
“We will be dealing with some new characteristics at the Circuit de Catalunya this year, because it has been totally resurfaced. We completed lots of test laps here during the winter and found the asphalt much less abrasive than it used to be. We also evaluated a number of new ideas on this circuit and have developed a softer range of compounds than we were accustomed to using in the past.”
“Although the surface has been modified, the track configuration means there is no change to the mechanically-induced loads the rubber must endure – and these are considerable. There are several long, fast corners that put a significant strain on tyres.”
“In addition, engineers run cars with a relatively high degree of downforce. Although this helps the tyres to generate more grip, it increases the demands imposed on the sidewalls through the higher-speed corners.”
“Last but not least, fuel loads are more influential here than at many other circuits – every 10kg equates to about 0.4s per lap.”

Driver perspective:
Fernando Alonso, Mild Seven Renault F1 Team
“Barcelona has traditionally been a tough circuit for tyres. Even though it has been resurfaced, I think it might be one of the first tracks where wear rates are a big concern for engineers, because the long, fast corners could make it very hard on tyres – especially the fronts.”
“From our perspective, though, we are very confident: Renault and Michelin have won four races out of four this season and, historically, we have always been quick in Spain. Everything is still there to fight for and I know the atmosphere will be fantastic – like a big party for all three days. That will be an even stronger motivation for me to fight for the podium.”

Technical focus
How track surface conditions affect grip Grip implies contact between two surfaces. On a racing circuit, the first of these is the tyre compound and the second is the track. The level of available grip will be determined by the nature of the track surface and its state of repair, plus its abrasiveness and the possible presence of rain.

To produce grip, a tyre needs a partner – the track surface – to stimulate the mechanisms that generate grip: a tyre’s ability to mould itself to surface imperfections and molecular adhesion.

Michelin refers to a tyre’s ability to adapt to variable road surface – when small surface imperfections dig into the tread – as “indentation”. Molecular adhesion necessitates direct contact between the rubber and the track surface, so conditions must be dry.

If water is present, it can be dispersed in two ways:

drainage (through camber, natural gradients or surface porosity)
storage (where water settles in ‘valleys’ below the level of any surface ripples).

Indentation can only occur when a track surface is reasonably abrasive – ie when it has a number of imperfections that will superficially impact on the tyre tread.

To determine the nature of the “indenters”, you need to measure the proportion of tread that is actually in direct contact with the track when compressed on its surface.

One method involves taking an imprint of the contact between the tread and the track. In the case of an F1 tyre, that figure rises to 30-70%.

Graphic: Measurement of the load bearing surface