Indianapolis MotoGP™ debrief with Masao Azuma
Bridgestone slick compounds available: Front: Soft, Medium, Extra-Hard. Rear: Medium, Hard (Asymmetric)
Bridgestone wet tyre compounds available: Hard (Main), Soft (Alternative)
Dani Pedrosa won his second race of the season at Indianapolis Motor Speedway last Sunday, the Repsol Honda rider winning the race ahead of compatriot Jorge Lorenzo on the Yamaha Factory Racing M1, while Monster Yamaha Tech3’s Andrea Dovizioso notched his fifth podium finish of the year.
Conditions over the race weekend were warm with track temperatures peaking at 48°C during the race. Grip levels were poor during the first day of practice on Friday and gradually improved over the course of the weekend though generally, the Indianapolis tarmac is towards the lower end of the scale in regards to outright grip. The tarmac at Indianapolis is also quite abrasive, so tyre choice for the race saw all riders selecting the harder front slick option, while the majority of works riders selected the harder rear slick, while most of the CRT riders went for the softer rear slick.
Pedrosa’s victory at Indianapolis means he closes the gap to Lorenzo in the championship to eighteen points, while Repsol Honda’s Casey Stoner remains in third place overall and thirty-nine points behind Lorenzo.
Q&A with Masao Azuma– Chief Engineer, Bridgestone Motorsport Tyre Development Department
Rear tyre choice for the race was almost uniformly split between the works and CRT machines. Can you explain why? “The Indianapolis circuit is quite demanding on tyres, particularly the left shoulder of the rear tyre which is put under extreme loads in the succession of fast left-hand turns. Our two asymmetric rear slicks that we supplied for this race have comparatively harder rubber on the left shoulder than the right, but almost every rider on the works bikes opted for the harder rear slicks. The reason for this is that greater power output and pace of the works bikes means the stress they place on the rear tyre is greater than the CRT machines, hence the harder rear option was chosen to ensure the best levels of durability and cornering stability.”
“The lower power output of the CRT entries means they generate lesser load on the rear tyre and hence riders on these bikes were able to go for the softer rear slick, which provides a slight trade off in durability for greater edge grip. However, the softer rear slick was still an option for the works riders with the right combination of setup and riding style, and Jorge Lorenzo was able to use the softer rear slick to ride his way to second place in the race. Additionally, both Colin Edwards and Steve Rapp on CRT entries preferred the feeling they got from the harder rear and so chose this option, so both rear slicks were viable race options for all of the riders on the grid.”
Special construction rear tyres were provided for the Indianapolis Grand Prix for the first time. How did these tyres perform and will you continue to provide this specification for this circuit? “The Special Construction tyres performed well, both by holding up to the tough demands of this circuit and also our rider feedback indicates the feel of these tyres wasn’t significantly different to the regular construction tyres we provided at this circuit last year. Our analysis of the tyres over the weekend, including right after the race, shows that the tyres were will within their operating temperature window despite the high track temperatures and extra loads generated by the latest 1000cc machines and so our decision to provide tyres with extra heat-resistance capability was the right move. Based on what we have seen last weekend we will definitely offer this specification of rear slick at Indianapolis in the future.”
Both the front and rear tyre compound selection was revised for Indy. Did these revised compounds perform as expected and what benefits did they provide to riders? “The Indianapolis circuit is very abrasive, yet provides relatively low grip levels so finding tyres that can generate adequate traction, yet provide the necessary abrasion resistance is quite a challenge for tyre development. For the front slicks we made the extra-hard compound available as last year we saw graining even on the hard compound front slick and so wanted to offer a front tyre with the best possible abrasion resistance. All riders evaluated this option prior to the race and the consensus was it did offer excellent abrasion resistance yet still provided enough edge grip to navigate the circuit with confidence, hence all riders selected this option for the race. For our rear slick allocation this year, we wanted to provide better edge grip to riders so we offered softer rubber compounds, though by supplying Special Construction rear slicks we could provide good grip levels while ensuring effective dissipation of the high level of residual heat this circuit generates.”