Conditions at Laguna Seca were typical for the California circuit with foggy and cool mornings giving way to sunshine and warmer track temperatures in the afternoon. For Sunday’s race conditions were fine and sunny with a peak track temperature of 50°C.

Q&A with Masao Azuma – Chief Engineer, Bridgestone Motorsport Tyre Development Department

Track temperatures in the afternoon sessions were quite higher than in the morning, what effect did this have on tyre evaluation and selection for the race?

Marc Marquez, Repsol Honda Team
Marc Marquez, Repsol Honda Team

Photo by: Repsol Media

“Yes the morning sessions on Friday and Saturday were very cool and track temperatures on both days went up significantly in the afternoon – this is quite typical for Laguna Seca. However, although track temperatures were reaching into the 40 degree range on Friday and Saturday afternoon, there was a cool breeze and this meant warm-up performance was still a critical point on these days. This had an effect on front tyre choice with riders using the softer front slick until they felt confident enough in the grip level of the track to move to the harder front slick option.

“On Sunday track temperatures were higher again and the breeze wasn’t as strong so none of the riders decided to use the softer front slick as warm-up performance wasn’t so important. The higher track temperatures on Sunday weren’t enough to persuade any of the works riders to use the harder rear slick for the race as barely any of them tried this option on Friday and Saturday, and they were confident in the performance of the softer rear slick even in higher temperatures. On the other hand three CRT riders did select their harder rear option for the race. Among the works riders only Stefan Bradl tried the harder rear slick on Friday and he felt that the greater performance of the softer rear slick offered more of an advantage over the greater durability of the harder rear. We saw last year that the race winner used the harder rear slick, but this year all works riders preferred the softer rear slick and this option worked very well over the race distance.”

The two harder rear slick options for Laguna Seca, the soft and medium compound slicks were offered in an asymmetric specification but the CRT-specific extra-soft rear slick was only offered as a symmetric option. Can you explain why?

“This year Bridgestone has four different rubber compounds for its slick tyres; extra-soft, soft, medium and hard. We use these four rubber compounds to create over ten different asymmetric rear slicks with different hardness rubber on the left and right shoulders. The naming convention we use for our asymmetric rear slicks is that the harder of the compounds used on an asymmetric slick forms the name of that option. For example, our soft compound asymmetric rear slick features soft rubber compound on the harder shoulder, paired with the extra-soft rubber compound on the softer shoulder. Our extra-soft rear slick is symmetric as we don’t have a softer rubber compound that we can utilise on the softer shoulder, meaning both shoulders make use of our softest and grippiest rubber. The CRT riders really like this option and most of them used this rear tyre during the race.”

Currently Bridgestone is providing riders with a greater number of softer rear slicks until a new hard compound rear tyre is developed. When will this new hard compound rear slick be introduced and will this see the normal tyre allocation return?

“Early in the season it was evident that a strong preference among the riders for the soft and medium compound rear slicks was occurring and the hard compound rear slick was not being used often. For whatever reason; be it an evolution in bike design or electronic controls, our current hard compound rear slick isn’t popular with riders this year, so we set about developing a new hard rubber compound. Until this change could be properly tested and introduced into the allocation, it was agreed that riders could choose a greater number of softer rear slicks at each race weekend. We are planning to introduce our new hard compound rear slick tyre at the Czech Republic Grand Prix next month and are hopeful that this new tyre will be well received. Bridgestone, Dorna and IRTA have come to an agreement that riders on MSMA machines can select up to eight softer rear tyres from the Czech Republic Grand Prix to last race regardless of the effectiveness of the new hard compound.”

Bridgestone MotoGP