Sepang MotoGP Test Tuesday Summary: Exploding Tires, Changing Compounds, & Stoner’s Return

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If being the official supplier to a racing series is a double-edged sword, then being the sole supplier of equipment as essential as tires is doubly so.

Leaving aside the complexities of exactly what a four-edged sword would actually look like, being official tire supplier to MotoGP is a role that offers massive opportunities for raising the role of a brand, and having it associated with the most famous names in motorcycle racing.

It gets your brand name and logo in front of many tens of millions of race fans and motorcycle enthusiasts every weekend. It also sees your logo plastered all over just about every photo which appears in magazines and newspapers about MotoGP, as well as filling thousands of column inches on websites and in magazines.

If you had to pay for the same exposure – a concept known as equivalent advertising value – it would cost you many, many times the €25 million Bridgestone were rumored to have paid for the contract.

There is a downside, of course. It is extremely uncommon to hear riders heap praise upon your tires spontaneously. Bridgestone had to announce they were pulling out of the role as official supplier to receive the praise they deserved, riders immediately paying tribute to just how good their racing tires actually are.

By contrast, criticism from riders about the spec-tire is both instantaneous and highly vocal. Allow a rider to speak about your tires, and they will expound in great detail on all of the failings, real and perceived, of the product you have so lovingly produced.

Should you suffer some form of catastrophic failure, or get something horribly wrong, then you face a barrage of coverage, all of it negative. As a tire manufacturer, you leave your PR people fighting fires for weeks, and sometimes months to come.

That is precisely the situation which Michelin finds themselves in this evening. At 10:40 on Tuesday morning, Loris Baz accelerated down the front straight at Sepang, and around two thirds of the way along, the rear tire of his Avintia Ducati GP14.2 exploded.

As Dorna only has a couple of cameras at the Sepang Test, the video coverage is mainly from the HD CCTV cameras around the circuit, one of which is permanently trained down the main straight.

The Big Bang

I was sitting in the media center working, and glanced up at the screen just before it happened, showing the image of the main straight. The ferocious bellow of a Ducati from outside announced the arrival of a bike at the bottom of the screen, and I saw a blue bike appear.

A fraction of a second later, the bike exploded, parts being strewn across the track. It looked terrifying, and I was almost equally shocked to see Baz standing at trackside, hanging over the armco with his helmet off, recovering his composure after what had been a massive off.

What followed was a chase for the cause of the crash. Journalists and photographers rushed outside to examine the wreckage, and try to put the pieces of the puzzle together.

There were four possible scenarios suggested by events: a blown engine, a suspension failure, a faulty tire, or a tire which overheated due to being underinflated.

The engine was the first theory to be discounted. There was a distinct lack of oil and engine internals on the track, and Ducati later announced that the engine was intact and fine.

I confirmed this with MotoGP Technical Director Danny Aldridge, who told me that the data showed there was nothing wrong with the engine when the crash happened.

Suspension failure was the next suspect to be crossed off the list, after Ducati pulled the rear shocks from all of the bikes and examined both the units and the linkages connecting them to the bike. The linkage on Baz’ GP14.2 was also fine, the only damage coming during the crash. It had to be down to the tires.

The Blame Game

This kicked off several rounds of pass the buck between Michelin and the Avintia team, which in turn upset the riders.

The track was initially reopened after fifteen minutes or so to clear the debris – Michelin meticulously collecting every scrap of rubber they could find, to ensure they trade secrets did not fall into the hands of their rivals – and then closed again a few minutes later.

Lengthy discussions ensued, before a decision was made to both withdraw the softer of the two rear compounds available – the A compound – and impose a higher minimum pressure for the rear tire.

Previously, the riders had been running with pressures of around 1.5 or 1.6 bar, but Michelin raised the minimum pressure for the hard rear tire – the B compound – to 1.7 bar. Once that call had been made, the track reopened, after having been closed for well over an hour.

Aleix Espargaro was less than impressed by the way the situation had been handled. “Michelin came to my garage and said, ‘No problem. You can go out and we’re working on it.’” Espargaro told us.

“I was really angry and I said to Michelin that I didn’t agree. For me they were doing really bad. Then I saw the green light. I was really angry so actually Tom [O’Kane] said to me, ‘Don’t worry. Take the leathers off.’ Then they put the red light again.”

It was clear to Espargaro what had caused Baz’s crash.

“I understood when they said that the Ducati was no problem it was the fault of the tires. Then they said to us to use the hard tire with more pressure. It was clear. The soft tire was too hot and then it exploded. For me we need to be a little bit more careful.” Marc Márquez agreed.

“Later I heard from the Michelin guys that they were not on the correct pressure of tire. For that reason there comes some blisters and then the explosion of the tire.”


Why was Loris Baz’s rear tire underinflated? Michelin pointed to the team, claiming they had asked for the specific pressure to be used on the rear tire.

The Avintia team pointed the finger at Michelin, saying that the Michelin tire tech in their garage had been managing tire pressures, checking them when Baz and Hector Barbera went out, rechecking them when the two Avintia riders came back in, and deciding which pressure to use while the bike was in the pits.

Baz had already had a problem earlier in the morning, a soft rear tire losing a big chunk of rubber from the surface. Yet he was sent out again later, and his tire exploded. The tallest and heaviest rider on the grid on the most powerful motorcycle was always going to place a massive stress on the rear tire.

It would have been extremely convenient for all parties involved (well, for all parties except the team) to blame the Avintia team. Either a faulty tire or a Michelin tire tech inflating the tire to the wrong pressure would reflect badly on the French tire maker, and cause the riders to lose confidence in them, before the season had even started.

Teams, especially underfunded teams such as Avintia, struggle to hire competent mechanics, and pay them enough to stay when they do. Avintia would be a convenient and credible fall guy for Michelin and the series organizers.

Yet it is Michelin who are ultimately responsible for the incident. The only person in the garage with a tire pressure gauge is wearing a Michelin shirt, and that person would have known exactly what tire pressure Baz had in his rear tire when he went out.

Dorna and IRTA have previously proposed the compulsory fitting of tire pressure sensors in MotoGP, but Bridgestone had rejected the idea on safety grounds when it was proposed.

Given that tire pressure sensors are now mandatory in Moto2 (made so after teams were found running dangerously low pressures in an attempt to improve qualifying times), that Aprilia and several other factory teams are currently running them, and in the light of Loris Baz’s horrific crash, they have a very strong case to introduce that proposal again.

There is a meeting of the Grand Prix Commission scheduled for Thursday, and it should be simple to dig out the old document and add it to the agenda. Rejecting it would not reflect well on the GPC.

From Soft to Hard

The aftermath of the whole tawdry affair was that the riders lost nearly an hour and a half of track time, including an hour of the best track conditions of the day, before the tropical sun raised surface temperatures and robbed the track of grip.

They were also forced to use the harder of the two rear tire options, which Aleix Espargaro believed was around a second slower than the soft tire. All of the riders were very enthusiastic about the softer rear, and were sorry to have lost it.

Using the hard tire made it more difficult to compare data from the first day, when most of the riders had concentrated on the softer of the rear options. Were changes in traction down to different set up, or the lack of grip from the B compound tire? It was hard to tell.

It meant that few riders managed to improve their times from the morning, leaving Danilo Petrucci sitting atop the timesheets. The Ducatis have been strong from the very start of the Sepang test, and five of them once again crowded into the top ten on Tuesday.

Jorge Lorenzo has been even stronger, the Spaniard dominating the first day, then getting to within six hundredths of a second of Petrucci using the hard rear tire, and leaving him second fastest on the day.

Cal Crutchlow was the second fastest man on a hard tire, ending the day in fifth, eight tenths behind Lorenzo. Valentino Rossi also impressed on the harder rear, finishing just behind Crutchlow in sixth.

New Fronts

It wasn’t just the rear Michelin tire grabbing the attention, as riders had also been given three different front tires to test. The reception was largely positive, though there were several crashes at Turn 5, a notoriously tricky spot for the Michelins: downhill, off-camber, on the gas with the rear pushing the front.

Neither Dani Pedrosa nor Pol Espargaro who crashed at the turn understood what had happened, the worst kind of crash for a rider. If you understand what went wrong, you can fix it. If you don’t know, you can’t do anything to try to prevent it.

The positive point of the front Michelin was that there was a little more feedback from it, making the limits a little easier to feel. The tire is also more stable, using a stiffer construction, allowing riders to brake a little more like they did on the Bridgestones.

It’s still not the same – Cal Crutchlow explained that the brake pressure was a lot less going into the corner, and mistakes on the brakes were a lot more costly on the Michelins – but it has made the tires a little bit more familiar.

The new Michelin front has also caused the Yamaha riders to virtually discount the 2016 chassis they had originally planned on running. It had been designed for the older Michelin tires, which the riders had been testing in 2015.

The improved front Michelin has caused Valentino Rossi and Jorge Lorenzo to favor the hybrid chassis, a bike which is much closer to the 2015 Yamaha M1.

It’s That Man Again

And of course there was Casey Stoner. The Australian proved that he was still fast enough to be competitive, setting the ninth fastest time on a hard tire, less than a tenth off the pace of Valentino Rossi and Andrea Iannone, and faster than the other factory Ducati rider Andrea Dovizioso.

He had no intention of returning to race, he emphasized, enjoying retirement too much and preferring to test. But he could not help himself but to rub a little salt in a couple of wounds.

“I’m not looking to put on a new soft tire and try to get a lap time,” Stoner said. “This is something that when you’re competing you get the urge to do, to crush the competition. I don’t need to at this point, so it’s literally getting as much data as we can.”

He made his commitment to being a test rider perfectly clear, however. He would continue to work on the Ducati GP15, leaving the work of developing the GP16 to the two factory riders.

The two bikes are similar enough that the data gathered by Stoner on the GP15 is just as useful as the GP16, and Stoner is aware of the sensitivities of the factory riders.

“We don’t really want to over-complicate things, and the riders want to do their testing with it first. Maybe I’ll get an opportunity in the future, but it’s better just for me to get accustomed with everything, start to learn a little bit of the progression, and when we find where we want to be with the GP15, not necessarily where the limit is but can feel we can’t go too much further, then maybe we will progress to the next version, and see how it works. But there’s a lot of time between now and then.”

Stoner rides again on Wednesday. The life of a MotoGP tester is not so bad after all.

Photo: FormulaMoto (Twitter)

This article was originally published on MotoMatters, and is republished here on Asphalt & Rubber with permission by the author.