Bridgestone Press Release: Hirohide Hamashima Talks About Graining At Indy

The Bridgestone press office issued the following press release after the Indianapolis round of MotoGP, in which they discuss the problems of tire wear encountered at the Indy circuit:


Indianapolis Grand Prix debrief with Hirohide Hamashima

Round 12: Indianapolis GP – Post-Race Debrief

Indianapolis Motor Speedway, Thursday 1 September 2011

Bridgestone slick compounds available: Front: Soft, Medium, Hard. Rear (asymmetric): Hard, Extra Hard

For the 2011 Indianapolis Grand Prix the infield section, from turns five to the final corner, had been resurfaced which left the tarmac much smoother than previously but provided several new challenges for the tyres and the riders. Ultimately, the new surface was much faster with a new qualifying record and lap record being set by Casey Stoner, who on Sunday also set a new fastest total race time, but at the start of the weekend it was very slippery and provided something of a moving target for the teams in terms of setup. Stoner romped to victory, his seventh of the season, ahead of Repsol Honda teammate Dani Pedrosa and American Ben Spies.

Hirohide Hamashima – Assistant to Director, Motorsport Tyre Development Division

What can you say about the new surface and what did it mean for tyre performance?

"The new surface started off slippery on Friday morning and because of this we experienced quite a bit of tyre graining during the first free practice, particularly of the rear tyres. The more laps were run on the circuit however, across all classes, the more conditions improved. The line became clearer and more grippy as more rubber was laid down on the racing line and this changed the challenge for the tyres and also the focus of bike setup. As the general grip level improved, rear tyre graining was reduced a great deal but as rear grip improved, many riders experienced the front tyre pushing and so front tyre graining and wear rate were higher, and this point in particular proved decisive in the outcome of the race. In fact, I can say that overall durability was good as many riders set their fastest laps towards the end of the race, including Casey's lap record on lap 20 and Andrea whose personal best came on the very last lap.

"The conditions over the weekend demonstrated very clearly the importance of a good rider and machine package in maximising tyre performance. Apart from Nicky, every rider used exactly the same tyre specifications in the race yet there were those such as Casey, Dani and Ben who were able to lap much more consistently than others and had a much better wear rate of their tyres.

"By the end of the race we could see just by the wear appearance of the tyres that the grip and character of new tarmac was much better, but I don't think it has reached its full potential yet. The wear appearance of the tyres, particularly from those at the front of the field, was the best it had been all weekend after the race so I think, bearing in mind how new the tarmac is and how little it had been used before this GP, IMS have done a good job in their resurfacing work."

What can you say about the tyre compounds Bridgestone selected for the Grand Prix?

"I am satisfied we chose the best-suited tyre compounds, front and rear, for this Grand Prix. In general, front tyre performance was good all weekend and we had no tyre problems. As the track condition and bike setups changed, different demands were placed on the fronts and in some instances this led to graining, but this is a symptom of the new track surface rather than a tyre issue and selecting different compounds would have made no positive difference. We will carefully analyse race tyre performance but based on the new surface we may revise the tyre severity rating for next year, although by then the character may have changed again so we will need to carefully consider this.

"For rear tyres, there were some rider comments on Friday, when the track was in its worst condition of the weekend that the extra hard compound rear was too hard to be used, but the balance at Indianapolis is one of tyre temperature. Even though the circuit was slippery, rear tyre temperature was very high, particularly in the left shoulders, and by the end of the race some riders experienced small blisters, which is incredibly rare. Had we chosen a softer rear compound, initial grip would have been improved but durability would have suffered meaning it wouldn't have been a suitable option for the race."

2011

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Comments

Had not yet realized the Repsol riders' fastest laps came so late in the race...amazing considering the conditions.

I've heard this word bandied around more this weekend than the rest of the history of G.P's and it annoys me. Mainly because I am unsure what they are referring to. I know what a normal wear pattern looks like on a slick (well I think I do, but these Bridgestones sometimes seem to be diametrically opposed to any other racing tyre ever manufactured).

Can anyone enlighten me as to what exactly graining is and how it is a detrimental feature?

I'm assuming it's the same as cold-tearing... the word "graining" seems to have crossed over from F1.

But I'm guessing, maybe it's completely different??

"It's called graining because the tire surface takes on a grainy texture. The soft, adhesive tread surface digs into the track texture, gets deformed into waves, and as sliding continues the waves turn over wearing rubber off the upstream side of the wave. When the sliding stops the deformed rubber snaps back leaving a peak pointing against the direction of travel. As more rubber is laid down during the race, grip will be reduced and there won't be enough side loading on the tread surface to start the wave formation"

http://insideracingtechnology.com/f1graining.htm

even though it's those god forsaken four wheeled things I've a better understanding.

We could also simply call it excessive wear. Although this appears to be an aggressive version thereof. Of course it's all about understanding the factors that contribute.

The speed at which you can tear up a tyre, compared to just wearing it, is gob-smacking. I have literally ripped through half the rubber on a supersport tyre in two laps of Phillip Is. It was a just rebuilt shock, had way too much compression damping on it, and I just did a couple of lap to get a first feel. Even after 40 laps at my pdestrian pace, regular wear will not be as bad because the tyre will still be smooth.

Here's the sort of thing I'm talking about, but I've seen worse:
http://www.motorcyclenews.com/upload/274333/images/tyre-doctor-cold-tear...

Oh, here's a front tyre version, pretty bad:
http://www.apriliaforum.com/forums/attachment.php?attachmentid=32102&stc...