The softer compound of F1 tyres

The softer of the two specification Bridgestone Potenza tyres used in the Malaysian Grand Prix featured a very different marking to that used in the first race of the season in Australia with the ‘white spot’ replaced by a ‘white groove’ for the second race of the year.

The softer compound of Bridgestone’s two Potenza tyres in Australia was signified by a 3 cm white spot on the tyre’s sidewall, whilst the softer compound in Malaysia featured a white groove after Bridgestone developed a more visible means of marking the softer tyres.

Normally racing tyres requiring marking would be marked when they are produced in the factory, and this is what occurs for the Champ Car World Series where a red tyre wall is found.

“The red tyre wall produced for the Champ Car World Series tyres is applied in the factory at the end of the production, at the time of the curing process,” explains Bridgestone Motorsport’s Head of Track Engineering Operations, Kees van de Grint.

This was not possible for Formula One as a change to the Formula One Sporting Regulations meaning that the two tyre compounds needed to be visually distinguishable from each other did not come until under two weeks before the Australian Grand Prix in Melbourne.

“As sole tyre supplier we produce the tyres a long time before the races and they had already been shipped to the various circuits when confirmation of the regulation change came so it was impossible to do anything in the factory,” said van de Grint.

Tests were undertaken to find a suitable paint and method of application and the white spots as recommended by the FIA were applied to the softer specification of Potenzas in use at Melbourne.

Whilst the white spot was visible when stationary, when the cars were moving this proved to be not the case.

“Let me say it performed well in Melbourne if you had extremely good glasses and you were very close to a car,” said van de Grint.

“In reality it was not visible for the people it was aimed for. I could see it, it was very helpful for me for example in parc fermé after qualifying. In a few seconds I could see the specification of each car but I was privileged to be maybe 50cm away from the cars. However, the people in the stands or the viewers on TV, they had no chance to see it so in that respect it was not a success.”

The group test held over 27th – 30th March at the Sepang circuit provided an opportunity to evaluate alternative solutions with larger spots and different colours considered.

“We always want to improve and we understand the importance of this for viewers and the media so we did four different configurations during the test. We found that painting the bottom of the tyre groove white worked excellently,” explains van de Grint.

With tyres allocated on event, tyre marking takes place as part of the tyre fitting process with white paint pens currently used to mark the bottom of the second from inside groove on both the front and rear tyres.

“Because the tyres were already made, we used markers with a special paint to mark them and this takes place after the tyre has been balanced, but is still on the balancing machine,” explained van de Grint.

“The tyre technician takes the marker and rotates the tyre by hand and with the other hand paints the bottom of the groove white. It is not so time consuming, because we can do it in about one minute. However the unfortunate thing is we have 616 tyres to mark at every race. That’s more than 600 minutes, or ten hours, worth of extra work for our tyre fitters.”

The plan is for the softer specification tyre to continue for the rest of the season with the bottom of the second from inside groove painted white.

“We will, of course, evaluate this after a couple of races and we are always looking for a way to improve. Eventually I expect we will find a way to do it in the factory, but for the time being the tyres are already made so we will continue to do it this way.”