Bridgestone's customary post-race press release after Argentina, complete with an explanation of the phenomenon of graining:
Argentina MotoGP™ debrief with Masao Azuma
Tuesday 21 April 2015
Bridgestone slick compounds: Front: Soft, Medium & Hard; Rear: Medium & Hard (Asym.) & Ex-hard (Symmetric)
Bridgestone wet tyre compounds: Soft (Main) & Hard (Alternative)
At last weekend’s Argentina Grand Prix Valentino Rossi won his second race of the 2015 MotoGP™ season with an emphatic victory while the podium was completed with Ducati Team’s Andrea Dovizioso in second place and CWM LCR Honda’s Cal Crutchlow in third.
The entire race weekend was dry yet the first day was marred by poor track conditions that resulted in low grip and accelerated tyre wear. Conditions improved as each session passed and although track temperatures reached 47°C during qualifying on Saturday, it was cooler for the race with track temperatures in the high-thirty degree range.
Q&A with Masao Azuma – Chief Engineer, Bridgestone Motorsport Tyre Development Department
The Argentina Grand Prix was the debut for Bridgestone’s new extra-hard specification rear slick. Did this option perform as expected last weekend?
“The extra-hard rear slick was developed specifically to meet the extreme demands the Rio Hondo circuit places on rear tyres and it performed very well level. There are two challenges at this circuit, extremely high temperatures on the left shoulder of the rear tyre, and high rates of wear on the right shoulder. With this in mind, using the data we acquired during last year’s race, we completely revised our rear tyre allocation for this year – the medium and hard rears this year were also different to 2014 - and also developed a new extra-hard rear. In regards to the performance of the extra-hard rear, Valentino Rossi showed the potential of this tyre by being able to lap quickly through the race. His second half of the race was particularly strong as set a new race lap record on the twentieth lap of the race and beat last year’s race winning time by four seconds.”
Given the strong performance of the extra-hard rear slick, was it the best race tyre for the factory Honda and Yamaha riders?
“Based on our analysis over the race weekend, our recommendation was for the factory Honda and Yamaha riders to use the extra-hard rear for the race but in the end each rider had to make their own decision based on their race strategy and bike setting. Making a final decision on race tyre choice was difficult for some riders as conditions for the race were cooler than on Saturday when they did their race simulations. Rossi’s quick, consistent pace on the extra-hard rear slick was impressive but Marquez also rode a very strong pace and challenged for the win on the hard rear. Also, Crutchlow was third and set his fastest lap on the last lap of the race with the hard rear, so it is obvious that this option also performed well. Tyre management in this race was key, with either rear slick option for the factory Honda and Yamaha riders capable of producing race-winning performance.”
In Free Practice 1 on Friday morning many of the riders experienced graining on their rear tyre. Can you explain what this means?
“Graining is a particular type of wear that is associated with a track surface that has very low grip, yet is abrasive. It causes excessive tyre wear and creates a rough appearance on the tread of the tyre. This phenomenon often occurs when there are large amounts of dust on the circuit which causes excessive spinning and slipping of the rear tyre. We expected graining to occur during the first session and knew that as more rubber was deposited on the racing line, the problem would go away. In the second practice session on Friday afternoon the graining was greatly reduced and by Saturday had completely disappeared and tyre performance returned to normal. The dirty track conditions that cause graining is something that occurs at racetracks that aren’t used regularly and therefore don’t have a clean racing line, the most obvious example apart from the Rio Hondo circuit being Qatar’s Losail Circuit.”