Bridgestone Press Release: Masao Azuma On How Tires Held Up On Indianapolis' Tricky Tarmac

Bridgestone today issued their customary post-race press release, discussing how their tires held up in the difficult conditions at Indianapolis:

Indianapolis MotoGP™ debrief with Masao Azuma
Wednesday 21 August 2013

Bridgestone slick compounds available: Front: Soft & Hard. Rear: Soft, Medium & Hard (Asymmetric)
Bridgestone wet tyre compounds available: Soft (Main), Hard (Alternative)

Repsol Honda’s Marc Marquez capped off an emphatic display of speed at Indianapolis MotorSpeedway by claiming his third consecutive MotoGP™ victory last Sunday ahead of teammate Dani Pedrosa and Yamaha Factory Racing’s Jorge Lorenzo.

Conditions at Indianapolis on Sunday were hot with a peak track temperature of 53°C recorded during the race and as fine weather persisted for the whole race weekend, the riders had ample opportunity to evaluate tyre choices before the race. All slick compounds in Bridgestone’s allocation for the Indianapolis Grand Prix being tested.

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

There was a lot of variation in tyre choice over the race weekend but for the race, no works riders selected the harder option rear slick.

“Indianapolis continued the trend we have seen throughout this season; riders are prepared to choose the softer rear slick option and devise a strategy to make it last the race distance rather than opting for the more durable, hard rear slick. It seems riders want the option that will give them maximum performance at the start of the race, rather than have a tyre option that will offer more consistent grip levels over the race distance. However, reviewing some of the rider comments after the race, I believe that some riders would have had good results had they chosen the harder rear slick available to them, as some did experience a marked drop in tyre performance in the final laps of the race on the softer rear slick. The Indianapolis circuit is very abrasive and the extra durability of the harder option may have offered more consistent performance over the race distance. The challenge for us at the moment is developing new tyres and looking at compound selection so that riders feel there is more of a benefit to selecting harder rear slick options for the race, and work in this regard is ongoing.”

So as all works riders selected the softer rear slick option for the race, how did this perform in what were quite hot track temperatures on Sunday?

“Actually the performance of the softer rear slick for the works riders, the medium compound tyre, was very good. Not only did Marc set a new race lap record, he did so on the eighteenth lap so this showed that the softer rear option exhibited good durability as well as performance so this was a positive for us. This year’s race was a lap shorter than last year, but in our estimation over the same race distance, the overall race time this year would have been about seven seconds quicker than last year – another positive sign. Despite the good performance of the medium compound slick tyre, the data we acquired during Friday and Saturday practice show us that the hard compound rear tyre was also a viable race option for Sunday, but as no rider decided to use it we were unable to make a direct comparison.”

Again this year there was a lot of talk about the track surface at Indianapolis. In regards to the tyres, what makes the tarmac of the Indianapolis circuit challenging?

“Indianapolis has three different types of tarmac; one type used on the oval course, one type on the section starting at turn one that was originally constructed for Formula 1, and the other type is on the infield. The infield tarmac is the most challenging in terms of tyres as not only is it one of the more slippery surfaces seen on the calendar, it is also quite abrasive. Usually if a tarmac is quite abrasive, you supply harder rubber compounds as hard rubber resists wear better. However at Indy we need to also ensure the rubber compounds offer enough grip to counteract the low grip level of the tarmac. It is managing this balance of resistance to wear versus grip at Indianapolis that makes it challenging for tyres. In addition to the tarmac, the layout of the circuit also adds to the challenge with the sequence of left-handed corners from turns twelve to fourteen generating very high temperatures in the left shoulder of the rear tyres. Because of this we employ our heat-resistant construction in the slicks we provide at Indianapolis. As you can see, the Indy circuit presents many challenges for our tyres but given the new qualifying and race lap records set last weekend and the overall tyre performance exhibited, I believe our tyre allocation for Indianapolis was well planned.

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I hope that this was not ‘mis-speaking’. Not only do we have a one-make series for tyres it’s a one-tyre series at each track this year.
We all know about the problems that Ducati and possibly every other team apart from Honda have at the moment, and perhaps Honda will run into problems at some point too (just like last year).
Bridgestone (or someone) needs to bring carcass options as well as compound. The problems Rossi is having and Burgess seems to be struggling with, is very much related to a softer, or less rigid, carcass. Something that is stiffer - perhaps like the one Stoner ‘liked’ before the current ‘softer’ version was introduced now seems to be necessary to meet the bike developments that have occurred since.
However, I’m not saying this because of Rossi - I would like to see each team have a tyre/compound that suits their bikes and each of their riders at each meeting. Only in this way will the playing field be levelled and allow a talented rider to use the equipment he wants/needs rather than is given.
I can understand why we perhaps do not want a return to ‘tyre wars’, but something better than the current status quo is deserved for teams and riders at this level. I certainly don’t want pit stops (!) but saying that they could have run the harder rear tyre seems a little perverse when people are asking for a stiffer front and yet they ignore them and don’t even mention that…..

The reality of allowing custom tires for the individual bike/rider combinations is that only the factory riders will get a wide range of tires to select from. Satellite team may get a few choices and the private teams will get the leftovers. The advantages that the factory teams will have will be even greater and competition will be reduced. The fast guys would be even faster with a greater differential between the fastest and slowest.

I suspect that if you pushed your thumb nail into either tyre you would think that there's not much difference.
I'm no tyre/asphalt expert but I imagine that , as it's old asphalt, that it has become worn/weathered, the bitumen has receded slightly, and the aggregate is not particularly grippy (I'm assuming it's not actually polished smooth by wear, as it seems Indy doesn't get much use in the infield -?) - the tyre therefore struggles for grip but the edges of the asphalt present a sharper edge to the tyre which shaves off the rubber.
This is a pure guess but the only explanation I have for that mysterious low grip/high abrasion factor!

The infield section that's complained about was repaved in 2011 (turn 5 through to 16). Maybe it's too new - and the surface instead of providing grip simply rips the tire up? I don't know. Indy did run more cars on the road course this year, and it seems to have helped some. Only one highside this year and not on that part of the track.

Lorenzo complained about the lack of grip/tire failure and the end of the race, and they did not addressed that. Maybe he was the only one complaining, but also Vale commented of lack of grip, well lets say, the tire started to slide, so it validates what JL is saying.

It looks like, either the tires didn't lasted enough, the M1 is destroying the tire or the tarmac is too abrasive for the compound.