From grooved tyres to slicks

In line with the new FIA regulations, from the start of the 2009 season Grands Prix are set to take place on Bridgestone’s slick Potenza racing tyres after the sport’s rules were changed to allow the return to slicks after eleven seasons of grooves.

Grooved tyres were originally introduced in 1998 as a means to slow cars down, which they achieve by having a smaller contact patch with the road for any given tyre size. When they were introduced, it was a new concept for motorsport, and one born of regulations rather than evolution. Since their introduction, Bridgestone’s grooved racing tyres have been raced at 188 Grands Prix and at countless Formula One tests over the past eleven years.

“Developing grooved tyres was very exciting for us back in the 1990s as we only had experience of slick racing tyres,” explains Hirohide Hamashima, Bridgestone 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 was 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 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 was a lot harder. The data we gained also proved to us that we needed a very strong construction of front tyre. We re-designed 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.”

Grooved tyres proved to be good for Bridgestone with the first pole position, race win and fastest lap all achieved in their very first race of grooves, the 1998 Australian Grand Prix.

Bridgestone and the Formula One teams and their drivers have worked with grooved tyres for over ten seasons now so the change in the regulations for next year means a lot of work between now and the start of next season.

“It is an interesting and significant development for Formula One to return to slick tyres. Formula One teams have been designing cars to work with grooved, dry racing tyres for a long time, so the information that teams previously held on running with slick tyres is completely out of date.” says Tetsuro Kobayashi, Technical Manager, Bridgestone Motorsport. Bridgestone itself has plenty of up-to-date experience with slick racing tyres as it produces slicks for many racing categories including karting, Formula 3, Formula Nippon, Japanese GT, GP2 Series and the IndyCar Series.

So, if slick tyres were banned from Formula One with the aim of slowing down cornering speeds, surely the re-introduction of slicks will mean the cars will go faster? “The 2009 regulations as they currently stand incorporate a number of elements to slow the cars down, most notably cutting the downforce levels significantly,” explains Kobayashi. "Also, the banning of tyre blankets means that drivers will certainly have to be more circumspect as they leave the pits and this will be another area of tyre management where drivers will have to be vigilant. On Bridgestone’s side we have changed the compounds to enable a lower temperature range for the tyres so that it is easier for drivers to get the tyres to their operating temperature quicker, and this is an area we will continue to work on.”

Teams have been testing Bridgestone’s slick tyres since early this year and have been running them at test sessions throughout the season. “We have plenty of data from these test and this includes all the driver comments given to our tyre engineers,” says Kobayashi. “We are always analysing the latest data which assists us in developing the tyres further.”

It’s all change again then for next season and Bridgestone’s focus is fully on developing their 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.”