Goodbye grooves - Bridgestone hail end of an era in Brazil 27 Oct 2008
This weekends Brazilian Grand Prix will see Formula One racing bid farewell to grooved tyres, a feature of the sport for the past 11 seasons. From next year, rule changes mean that teams are set to use slick rubber for the first time since 1997.
Grooves were introduced as a means to slow the cars, which the tyres achieved by having a smaller contact patch with the road for any given tyre size. A smaller contact patch not only means less grip, but also that the rubber that is in contact with the road has to be harder.
After the Interlagos race has played out, Bridgestones grooved racing tyres will have been used at 188 Grands Prix and at countless Formula One tests over the 11 years. When they were introduced it was a new concept for motorsport, and one born of regulations rather than evolution.
Developing grooved tyres was very exciting for us as we only had experience of slick racing tyres, explains Hirohide Hamashima, Bridgestones director of motorsport tyre development. We had the challenge of developing a tyre with a hard compound because of the structure and tread profile of the tyre, but one which gave the good grip required for Formula One.
From an engineering perspective it has been a very interesting aspect of our motorsport activities. We began testing our first grooved tyres in 1997 with Damon Hill. The first tyres were a modified slick tyre to let us understand the differences and requirements of a grooved tyre. We soon found that the wear rate on the front tyre was very high, and we experienced a lot of graining, so the compound we used for this tyre would have to be a lot harder.
The data we gained also proved to us that we would need a very strong construction of front tyre. We redesigned the size and shape of the front for a wider tyre and one with a larger diameter. This worked very well and we could manage car behaviour better than with the previous size.
The changes to the regulations for 1998 were not limited to the introduction of grooved tyres. They also saw the implementation of narrower cars to reduce downforce. The changes presented the teams designers with many challenges.
One of the teams we were going to supply for 1998 was McLaren and their car had already been designed for the smaller front tyre size, explains Hamashima. We had a lot of discussions with their chief designer, Adrian Newey, about this as he was very insistent that he wanted to keep the smaller size. However, after the first test he accepted the concept and modified the car.
Grooved tyres proved to be good for Bridgestone, with their first pole position, race win and fastest lap all achieved in the very first race of grooves, the 1998 Australian Grand Prix. These feats were all accomplished by McLaren driver Mika Hakkinen, who went on to take the world championship that year - the first to be won using Bridgestone tyres.
1998 is a very memorable season for us, says Hamashima. We faced a competitor, Goodyear, which had been in Formula One for many years, but there were new regulations and we gained the advantage.
For the next two seasons, Bridgestone was the only tyre supplier for Formula One racing, and this brought the additional test of supplying all of the teams on the grid with grooved tyres.
We faced a big challenge for 1999 as we found ourselves supplying all of the teams in Formula One, and this was a big logistical step for us, explains Hamashima. Then we faced a stronger challenge when a new and hungry competitor entered Formula One.
Michelin came into the sport in 2001 and the development of grooved tyres really took off.
The competition between our two companies was intense and our understanding of these tyres increased at a rapid rate, says Hamashima. We developed a new construction concept which allowed good grip but less wear to counter the grooved tyre characteristics, and we had a big battle with our rival tyre manufacturer with this tyre.
How a grooved tyre interacts with the road is different from the way in which a slick tyre works and for the drivers it was a new sensation.
Driver comments when we moved to grooved tyres were not so favourable, explains Hamashima, as drivers always want more grip, and grooved tyres, by design, have less grip. Also, grooved tyres mean that graining is far more likely and this means something else that drivers have to control in their tyre management.
Graining, where sideways forces mean the rubber rolls across the tyre, changes the grip characteristics of the tyre when it is occurring.
Graining is more common on grooved tyres as the compound is harder and more difficult to get working on a dirty track, explains Hamashima. The grooves also mean there are many edges on the tyres for the raised areas. Slicks are less susceptible as there are no edges, the compound is softer and theres a bigger contact patch.
Bridgestone was once more the only tyre supplier in Formula One racing for the 2007 season. When we provide tyres to all teams the philosophy is different, explains Hamashima, as we are no longer constantly developing compounds and constructions to make faster tyres. Instead, we work to ensure that our tyre supply is fair and our tyres are consistent for all teams, for example, by providing tyres for each race which are made in the same batch.
Bridgestones supply of grooved tyres to all teams through 2007 and the current season (the first of three with Bridgestone as the official tyre supplier to the FIA Formula One World Championship) has meant lap times have got closer and closer.
We saw at the start of the 2007 season that some teams quickly understood how to maximise the potential of the different compounds and the strategy options these allowed, whilst some teams took longer to develop their understanding, says Hamashima. However, as we approach the end of the 2008 season we can see that there is very good understanding of our grooved tyres by all teams and lap times can be very close.
Its all change for next season, however, and Bridgestones focus is now on slick tyres. The return to slick tyres means we can apply the lessons learnt from grooved Formula One tyres to slick Formula One tyres, says Hamashima. 2009 should be a very interesting season.