The following is from Bridgestone…
This year’s Spanish Grand Prix at Jerez took place under resplendent sunny skies and saw local hero Dani Pedrosa ride to victory ahead of his Repsol Honda teammate Marc Marquez and Yamaha Factory Racing’s Jorge Lorenzo in third place.
The warm and sunny conditions presented the hottest track conditions at Jerez in years, with a peak track temperature of 53°C during the race providing a stern test for the riders, machines and tires.
Q&A with Masao Azuma – Chief Engineer, Bridgestone Motorsport Tire Development Department
Track temperatures were the highest they’ve been in recent years at Jerez, but all riders chose the softer rear slick options available to them. Can you explain the reason for this?
“To see track temperatures in the mid 50°C range at the first race of the European season is unusual, but the harder rear slick options we brought were for such a possibility. With such high temperatures, it was expected that some riders would select harder rear slicks for the race, but the greasy track conditions meant riders chose softer rears to give them the highest level of cornering grip. Some riders did comment that the drive grip, that is the grip when the rider picks up the machine from full lean angle when accelerating out of corners, was better on the harder rear slick, but edge grip, which is important at the flowing Jerez circuit, was better on the softer rear option - even in the very hot temperatures. Race simulations in practice revealed that the rate of wear on the softer rear slicks was sufficient for the race distance, and this is why every rider selected the softer rear tire on Sunday.
“The fact that the wide operating temperature range and durability of our softer rubber compounds provided consistent performance over a race distance is positive for us. We had a similar situation at Austin two weeks ago. At that time only two riders selected the harder rear for the race, but the difference is that one of these riders ended up winning the race! In this case riders could lap at a similar pace with harder rear tire, whereas at Jerez they could not. We believe this was due to the character of the tarmac and the very high track temperatures in Spain. We will now analyze the data we have from the race to see if there are any lessons to be learned for our future tire development and race compound selection.”
Front tire choice was also uniform across the grid, but in this case the riders selected the harder option, medium compound front slick. This seems at odds with the rear tire selection.
“Just as the layout of Jerez requires a high amount of edge grip from the rear tire to maintain good corner speed, it also requires a great deal of stability from the front-end under braking and cornering. Also, when you consider that track temperatures at the beginning of last year’s race were 30°C cooler than this year, we must also consider warm-up performance, so our front slick tire compounds for Jerez were the soft and medium compounds. The high track temperatures we experienced this weekend meant that warm-up performance wasn’t such an important factor and so rider choice shifted towards the harder front slick option to give them the most front-end stability. Even though the track conditions were challenging, there isn’t a big difference in overall grip level between our two front options at Jerez, so riders chose the option that gave them better stability in braking and especially cornering.
“Some riders did comment that they would’ve liked a harder front tire at Jerez this year, but considering the exceptionally hot weather compared to previous years, I think the balance of our compound selection was correct.”
We are three races into the season and each race has presented markedly different track and weather conditions. Have you learned anything new about the performance of the 2013 MotoGP machines that could contribute to a change in future tire design?
“We are constantly collecting and analyzing tire data, telemetry and rider feedback as part of our MotoGP tire development program. As we know, the machine weight has increased by three kilograms this year, and so we are investigating what affect this change - plus the fact that teams have now had a year to develop their chassis, electronics and power delivery to work with our latest generation of MotoGP tires – has had on tire performance and will apply these lessons to the development for our next generation of tires. After pre-season testing and three races we now have a substantial amount of data with which to start developing the tires for the 2014 season, which we will present to riders for evaluation later in the year.”