This year Bridgestone brought their asymmetric rear slicks to the United States Grand Prix and as well as being welcomed by the riders they contributed to a new lap record and a fastest total overall race time.
Jorge Lorenzo took his sixth victory of the season after Dani Pedrosa crashed out to extend his championship lead to 72 points before the summer break. All riders used the softer rear Bridgestone slicks, and Mika Kallio, Alex de Angelis and Alvaro Bautista were the only riders not to opt for the harder front tire.
Q&A with Tohru Ubukata – Manager, Bridgestone Motorcycle Tire Development Department
Q. What can you say about the performance of the asymmetric rear slicks this year?
Tohru Ubukata says: “I think that the numbers speak for themselves in terms of the improved performance that the asymmetric rear slicks offered at Laguna. Both Casey and Jorge lapped faster than the existing lap record, Casey’s fastest was 0.5seconds better than the best lap from last year’s race, and the total race time was over six seconds faster than the previous best. This indicates not only better outright performance but better durability and consistency too so I am very happy.”
“All riders preferred the softer option rear which in the conditions we experienced during the weekend performed better than the harder option, which gave a combination of better grip and better durability. To have set another new lap record is a good success for us and it is the sixth new lap record from the first nine races of the 2010 season.”
Q. Why weren’t asymmetric rear slicks selected for Laguna Seca last year?
Tohru Ubukata says: “Laguna Seca does have more left-hand corners than rights but it is not a typically asymmetric circuit – that is to say the difference in temperature and wear rate between the two rear tire shoulders is not significant. When tire temperatures are markedly higher in one shoulder than the other, this is when we use asymmetric tires to equalize tire temperature in each shoulder using a combination of harder and softer compound rubber. The difference in tire temperature between the shoulders at Laguna however is fairly small – what we would normally cover with symmetric tires. However, last year the riders expressed a great desire for asymmetric tires at Laguna Seca, so we brought them this year to give the riders more confidence to push hard and attack.”
Q. What about front tire performance during the race?
Tohru Ubukata says: “The majority of the riders used the harder option front slicks but Mika Kallio finished ninth using a softer option front, so this shows that both specs were working well. During the race many riders reported a feeling of closing the front, or movement in the front tire under braking and corner entry, but the harder option provided more stability than the softer which is why it was ultimately the faster choice, and we can see from the laptimes that performance was still good. There were some crashes during the race, but Hector retired with a broken chain and Alvaro fell as a result of contact. Dani, Marco and Aleix all fell at the left-handed turn seven and reported the bumps to be the cause.”
Bridgestone slick compounds available:
Front: Medium, Hard.
Rear: Medium, Hard (asymmetric)