The 2015 MotoGP championship is one of the closest in years. Close championships are always fascinating, but this one has an extra edge to it: the two men fighting over the 2015 title are both teammates, and racing on the same bike. The differences between the Yamaha M1s of Valentino Rossi and Jorge Lorenzo are virtually non-existent, their results dependent entirely on the riders themselves, and how well their teams prepare the bikes and riders for the race.

With nothing to choose between the bikes, focus has turned to the tires. Jorge Lorenzo's constant references to his preference for the tire with the special edge treatment have made this focus much keener. Under the glaring spotlight of public scrutiny, the allocation of tires which Bridgestone brings to each race has taken on the appearance of being the decisive factor in every race. Before every race weekend in MotoGP, the one question I get asked most via Social Media (other than "who do you think will win?" of course), is whether Bridgestone will be bringing the tires with the edge treatment or not.

This focus on tires is becoming so intense that a number of misconceptions about Bridgestone's rear tires are starting to arise. Some fans are starting to believe that Bridgestone are manipulating the results by bringing the special tires to some races, but not to others. They are starting to believe that tire choice is the sole deciding factor in races. They are even starting to believe that Jorge Lorenzo is the only rider who likes the tires with the edge treatment, and that those tires are an actual disadvantage for most, if not all of the other riders on the grid.

That tires have been a factor is something I have been keeping an eye on for a while. I have had numerous discussions with Bridgestone staff throughout the year, questioning them on the circumstances and process behind the tires and tire choice. At Silverstone, I also questioned a number of riders on how they feel about the tires, and whether they prefer the tires with the edge treatment, or are hindered by them in some way. Given the stakes, I did not ask Jorge Lorenzo or Valentino Rossi about it, but instead got a range of riders with different manufacturers to give their opinions.

But first some history, and an explanation of how we came to this point with the tires. In 2010, Bridgestone came under a lot of pressure to start changing their tires, to allow them to warm up more quickly. Temperatures were unusually cool that season, which caused a spate of cold tire highsides, resulting in some serious injuries. The most high profile of those was Rossi's crash at Mugello, where he broke his leg and was forced to miss three races as a result, others suffered too, such as Hiroshi Aoyama, who fractured his vertebrae, an injury which affected his riding for a very long time.

From that point, Bridgestone worked on making a tire which came up to temperature quickly, but the changes they made came at the same time as MotoGP was preparing to switch back to a 1000cc formula in 2012. The new bikes were heavier, faster, and more importantly, had more drive further down the rev range. Combined with the huge steps forward made in electronics during the 800cc era, this generated significantly greater loads on the tires than Bridgestone had expected. More mechanical grip from the bikes, and better grip from the added weight and new tire design caused the tires to start showing signs of overheating, a tendency which was exacerbated by the increasing role of electronics.

The extra grip available prompted factory electronics engineers to try to exploit that, using electronics to try use the grip and prevent the tire from spinning. When a tire spins, it heats the surface layer; when it grips and creates drive, it heats the carcass of the tire. Surface heat from spinning dissipates rapidly in the air. Heating the carcass means heat throughout the tire, and nowhere for that heat to escape.

There followed a vicious circle. As the factory engineers adjusted their electronics to exploit the grip, the tires would spin less. That meant that Bridgestone could use a softer rubber compound, as the harder compounds were not needed to cope with tire spin. Softer rubber created more grip, which prompted the factory engineers to adjust the electronics even further to use that grip. Load on the tire shifted ever further inward, from the surface to the full carcass of the tire.

Inevitably, something had to give. Tires started developing anomalies, and at Assen in 2012, serious problems developed, rear tires shedding chunks of rubber. Ben Spies finished a long way from the podium with rubber coming off his tire, and Valentino Rossi was forced to pit for tires. Tires coming apart was not an acceptable situation, and so Bridgestone needed to find a cure.

That cure came in the form of what is now known as the heat-resistant layer. Bridgestone, through a secret process, managed to insert a special layer in their tires which prevents the inner carcass from overheating. The interior of the tires dissipated the load better, solving the problem of tire chunking. In 2013, Bridgestone brought those tires only to a few tracks, such as Mugello and Assen, where the danger of tires losing rubber was particularly high.

Yet again, the vicious circle of tires and electronics kicked in, loads and tire temperatures increasing at other tracks as well. At the end of 2013, Bridgestone decided the safest course of action was to bring the heat resistant tires to all of the tracks. The trouble was, using the heat resistant layer at tracks with cooler temperatures or lower loads altered the behavior and feel of the tires. There was less grip on the edge of the tire, and as a consequence, less feedback from the tire at full lean angle. For riders who use a more point-and-shoot style, there was no discernible difference, but riders whose style was based around carrying corner speed were hit harder, as they could no longer feel just how much grip there was on the edge of the tire, as they had the year before. Jorge Lorenzo, the king of corner speed, was particularly badly affected, his style rendered ineffective at a stroke.

Bridgestone looked for a solution, and by mid-2014, they hit upon applying a special treatment to the tires to give the edge of the tire the same feel as if softer rubber had been applied. They basically recreated the feel of the non-heat-resistant tires from 2013, while keeping the heat resistant layer. The edge treatment tires were not needed at every circuit – tracks like Assen, Mugello and Indianapolis place enough load on the tire that they behave like the 2013 tires without it.

2015 is the first year where the combination of heat-resistant layer and edge treatment has been used for the full season. At the end of 2014, Bridgestone sat down and mapped out which tracks would need the edge treatment and which wouldn't. That schedule has been followed ever since, adjusted only as they have brought new developments to their tires, a process which is ongoing and the reason they go racing.

But it has also meant that some riders, and Jorge Lorenzo in particular, have been vociferous in complaining when the non-edge-treated tires are brought to tracks where they don't work as well as the edge-treated tires. This, in turn, has created the illusion that Jorge Lorenzo only wins on the tires with the edge treatment, and hence that Bridgestone favors Lorenzo, and that those tires are a disadvantage to the rest of the grid. This conveniently ignores the fact that Lorenzo dominated at Mugello on tires without the edge treatment, and only narrowly lost out to Marc Márquez on the same tires.

So how do the rest of the grid feel about the tires with the softer edge? Opinions are mixed. Some riders say that they cannot feel the difference between the tires with and without the edge treatment, while others have a distinct preference for the softer edge. Nobody I spoke to positively dislikes the edge-treated tires, and the Suzuki riders, in particular, are extremely enthusiastic about them. This is hardly surprising, given the Suzuki's reliance on corner speed for its performance.

Andrea Dovizioso was one rider for whom the tires made no real difference. "I never feel the difference," Dovizioso said. "Every rider is different, the riders feel everything in a different way, with the same bike with the same tires. I really don't feel a big difference." There are factors which play a much greater role, the factory Ducati rider said. "The difference for me is about the asphalt you find in a different track, the temperature. For my style this is a much bigger difference."

Honda riders Dani Pedrosa and Cal Crutchlow preferred the edge-treated tires. "The edge treatment can help," Pedrosa said. "Last year we didn't have it, this year we do, so that can help. Maybe that's an advantage over the last year, and maybe we can manage better that lack of grip."

LCR Honda's Crutchlow was even more positive. "Honestly, sure, we all prefer the edge grip. I don't know a rider that doesn't prefer the edge grip. Because you know riders, what are they complaining about? It's grip, it's the only thing that holds you to the ground. Sometimes with the Honda, we don't mind to slide to turn the bike, but still, if they ask do you want the edge grip or no edge grip, we ask for the edge grip."

What Crutchlow was less enamored of was the heat-resistant layer inserted into the tires. "What we all hate is the heatproof protection. Every tire has the heatproof protection on, because they're scared of the tire getting overheated, but in the days when there were no heatproof tires, they were a lot better. A lot better to ride, much more fun." The risk was just part of racing, and managing the risk of tire damage was the responsibility of each rider, Crutchlow believes.

Bradley Smith also preferred the tires with the edge treatment, but he had a slightly different perspective. Though the edge-treated tires were definitely better, the Monster Tech 3 Yamaha rider felt he could close the gap to the front runners more when Bridgestone brought tires without the edge treatment. "I like the soft edge, but I like the other one as well. I would probably say I'm closer to the other riders without the soft edge, because maybe it suits my riding style a little bit more, pick it up, get it off the side of the tire. I don't mind the bike spinning around as much beneath me, where others like it be on rails all the time. So when it's not there, I'm sometimes closer to the other guys than when it is, so for me, it's either or."

Smith also had an explanation for why Lorenzo prefers the edge-treated tires. "It's more about how the tire works with his riding style, at that moment, how he has his bike setting, things like that. You've got to bear in mind his setting is more on the nose, so when he doesn't that have that soft edge, then the bike slides around more underneath him. My setting is to have the bike more on the rear anyway, so the hard edge for me is sometimes a blessing."

Will Bridgestones tires end up deciding the championship? In as much as tires always decide the championship, then they will. Does Bridgestone bring tires especially for Jorge Lorenzo, tires which the other riders hate? Bridgestone puts their tire plan together at the start of the year, and deviate from it very rarely. The other riders are just as keen on the tires with edge grip as Lorenzo is, but are not able to exploit them to the extent that Lorenzo can. Nor have these tires been developed especially for Lorenzo's riding style. If anything, the 2015 Bridgestone tires – with heat-resistant layer, and with the treated edges for a softer feel – have been designed to recreate the feel of the 2013 and 2014 tires, without the heat resistant layer.

Are the Bridgestone tires having an effect on the championship? Absolutely. But as we saw in Silverstone, different conditions and a change in the weather can radically shake things up. With six races to go, a title chase as close as this is far more likely to be decided by random events – a bout of 'flu, a lapse of concentration, perhaps even something mechanical such as a sticking brake or incorrectly adjust shift lever– than by whether Bridgestone brings the edge-treated tires to a particular race.

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