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27 Aug 2015

Pirelli, are the marmite of Formula One, although it seems that most want to blame them for all of the sports ill's.  Just like the goalkeeper nothing is mentioned of the good work they do until something goes wrong.  And, just like the goalkeeper they are not always to blame, he has 10 other players in front of him all of which have given the opposition the chance to score.  In this, perhaps tenuous analogy Formula One teams are much the same, they're the outfield players looking for someone to blame when the chips are down.

Sebastian Vettel's rant to the BBC in the bull pen after the race once again divided opinion, there are those of us who believe that Pirelli get far too much flack for providing a product to the specification that the regulatory body asked for.  Meanwhile, you have the Ferrari and Vettel supporters who are angered by the fact their driver lost out on a podium.

So, lets be pragmatic and try to understand what happened and more importantly why.  Firstly what did Sebastian actually say, for those that missed it or have only heard selective elements of the interview, note the quote I have highlighted in yellow for post interview reading:


Lee McKenzie: "Sebastian, do you think Ferrari were being a little too greedy in the end, do you think?"
Sebastian: "No"
Lee McKenzie: "So you were happy with the decision and you wanted to stay out? You could have got to the end you felt?"
Sebastian: "Well how many laps I was missing, not many and things like that are not allowed to happen, full stop.  If it happens 200 metres earlier, I'm not standing here now, I'm with 300 stuck in Eau Rouge, so I don't know what else needs to happen, ermmmm, yea."
Lee McKenzie: "So in that case then you're obviously upset that the tyre went that way, but you'd run it for 27.."
Sebastian: "I'll tell you what is upsetting, upsetting is that one thing is the result, you know this is racing, for sure we deserved to finish on the podium but the other thing as I said is this happens earlier, you know, I don't you know [sighs and doesn't commit to the rest of the comment].  I think it's a sort of theme that keeps going around, no-one is mentioning but it's unacceptable."
Lee McKenzie: "You were one of the drivers that stated their concerns to Charlie Whiting in the drivers briefing.  Was that taken seriously?" (referring to the Rosberg tyre incident during FP2)
Sebastian: "Well I think it was, but what's the answer? Same as everytime, yea well there was cut / debris, there maybe something wrong with the bodywork, the driver went wide bullshit, if Nico tells us he didn't go off the track, he didn't go off the track.  Why should he lie to us? It's the same with me I didn't go off the track, it's just out of the blue, the tyre explodes and as I said if this happens earlier I'm in shit."
Lee McKenzie: "But you drivers must be the ones in the power seat, so what do you do now before Monza?"
Sebastian: "I think we need to speak to each other (the drivers), it's probably not as bad as it was in Silverstone some years ago, but it's not acceptable."

Now I'm sorry Sebastian, I have the utmost respect for you as a driver and have often defended you when others have called into question your ability but, as you did I call bullshit too.  You were clearly off the circuit on numerous occasions as we can see below...

Lap 31 - We'll start here as everyone can call out Sebastian for being off the circuit at Raidillon but here at Stavelot the Ferrari driver frequently exceeded the track limits.
On lap 33 the BBC cut to a slow motion replay provided by FOM of one of Sebastian's off track excursions at Raidillon.  The arrow points to the location of a sausage kerb that was removed after FP2 as the drivers aired their concerns over safety.  I completely understand their logic a raised element there is asking for a disaster IF a driver gets his line wrong.  The problem with its removal is that it allowed drivers to overstep the track limits.
Same picture but I wanted you to also note the dynamic platform of the car at this stage, take a look at the right rear wheel.  It is completely airborn, as the car takes off over the kerbing, rotating at full engine speed, the tyre impacts with ground in the next image
The tyre has now come to rest on the ground, a peak loading placed on the tyre in doing so will not only aggressively heat the surface of the tyre but send a shockwave through its carcase.
Vettel isn't just over the track limits here, he has all four wheels almost a tyres width off the circuit

You'll note that the forces placed on the tyres carcase means the sidewall of the tyre is about to bulge
Out of shape you can now see the tyre lifting away from the outer wheel lip
Actually now in the apex of the off his off circuit exploration the platform of the car is fairly stable again
However, that's not the end of the problem as the kerb has a transition in its surface as you round the corner, not a problem if your on the correct side of it but Sebastian is not.  He's about to exert force on the tyre again, just after the last episode and this time in a short, sharp stab.
As we can see the outer juncture where the tread platform meets with the sidewall takes the hit, deforming the sidewall.
The tyre once again undergoes a deformation, with the tyre moving away from the wheel lip.  Furthermore the car is destabilised meaning the car is scrabbling for traction at a point when Sebastian is trying to apply as much throttle as possible (full).
The tyre is now completely warped, creating a sort of wrinkle, wherby the tyre is trying to catch up with itself.  The structure being pulled both longitudally and laterally.
Still warped....
Still warped, starting to settle..
Back to its natural state but the amount of energy that has been put through the tyre has been huge
As we continue to follow Sebastian on lap 34 he's wide again through Stavelot
This time through Eau Rouge we're onboard with the thermal imaging camera, he doesn't step fully over the kerb this time, probably knowing a repeat infringement will have Charlie on the blower with a warning
Lap 36 at Malmedy and Sebastian is again playing with the track limits, in an attempt to lower the aggravation to the tread platform

Lap 36 down at Stavelot again...
Lap 42 - Just before the tyre let go and Sebastian is once again all over the kerbing at Raidillon
Lap 42 mid corner and Sebastian is clearly trying to cut as much of the corner as possible in order that he doesn't get caught by the chasing Lotus who'll also have DRS assistance along the Kemmel straight.
As he leaves the corner the car is once again off balance having clipped the exit kerbing, with the tyre trying to make its escape from the outer lip
In fairness to Sebastian as Romain tries to catch the Ferrari driver he too cuts the corner at the top of Radillion

Track Limits

As we can see the tyre 'explosion' on Sebastian's car was aggravated by a constant abuse of track limits.  Had the sausage kerbing not been removed from the circuit at Raidillon (at the driver's request) I don't think we'd have seen the issue at all, furthermore I think Ferrari would have been forced to two stop.

With the sausage kerbing in play during FP2 Sebastian was much more reluctant to stay left over the crest
The kerbing forces the driver to take a tighter line up through Eau Rouge as touching the sausage kerb on the left would not only slow and unbalance the car but if repeatedly undertaken likely result in suspension damage.

This is a source of great frustration to many people, for the drivers we may aswell take their machinary to Santa Pod and see who's is the quickest in a straight line, as it appears that no corner or obstacle is sacred in their desire to make their own lives easier. It's Eau Rouge for Christ's sake, a corner you should dare to drive, whilst on Sunday its challenge was lessened as the drivers (not only Vettel) straight lined Raidillon with the sausage kerb being removed on safety grounds.  They would argue that they gained no lasting advantage by straight lining the corner and the data would probably support that, but that is because a) they were all at it, making any advantage null and void and b) the advantage was not supposed to be a direct consequence of laptime but rather them stressing the tyres less over the stint length, increasing its longevity.  The drivers also know that for Race Control to issue a warning and/or penalty for track limits there needs to a) be a serious breach that has led to a lap time gain, b) constant abuse of the limits, something you could argue Sebastian was guilty of, although he did take car not to straight line Eau Rouge every lap and c) consistency: the drivers know that if they're all doing it, very little can be done, as a penalty to every driver simply retains the status quo.


Radio communique

Did Sebastian question the strategy? We got the following audio around lap 29, just when FOM were starting to concentrate on the battle between Sebastian and Romain, although it's likely it came a lap or so earlier. 

Sebastian: Think about the next stop, make sense?
Engineer: Ok, we are looking into it... Tyres from the data looks pretty good, to go to the end

I think the statement can be taken one of two ways, considering the way teams try to bluff one another.  Personally I think it was a call by Sebastian to insinuate he was thinking about a stop, as Lotus would then undoubtedly reign in Romain, thinking he wouldn't need to make the pass on track.  This would invariably give the German a little breathing room and continue to run the pre meditated one stop strategy work.

But didn't Hembrey say the tyres should be able to do 40 laps around Spa?

In a post GP interview with Ted Kravitz, Paul Hembrey did concede that they were targeting a maximum of 40 laps for the Prime (Medium) tyre around Spa.

Ted Kravitz: "So what did you estimate the wear life to be and he did 27 I think laps on them"
Paul Hembery: "28, we thought the strategy was going to be based 2/3 stops as you saw the majority did, but they felt, clearly they could make it work on the one stop. The wear life was indicated at around 40 laps but that's an indication, you know, race conditions can change that and some factors involved in racing mean that sometimes that is not a precise datum and other teams were clearly taking another direction."

Now, whilst most jumped on this an opportunity to jump down the throats of the beleagured tyre supplier I find myself in their corner again once again.  Firstly note Paul's cavaet that seems to have alluded everyones attention 'around' 40 laps, ie not 40 laps.  In any case the only teams I could foresee doing 40 laps on the Medium around Spa would be Manor and McLaren, given their lack of pace compared with the rest of the field.  It was clearly a two-stopper, but Ferrari thought otherwise and in fairness to them they would have had a Pirelli engineer with them suggesting that it's possible.

This is part of a larger, more worrying issue that I have mentioned before, the teams are driving as slow as possible in order that they make less stops.  After all there is a time loss during a pit stop which can be offset by time lost on track by not stopping.  In the case of Spa, that pitlane delta is +/- 22.5 seconds (depending on the time in box) meaning you can do 22 laps at a second a lap slower than your opponent who's stopping once more all whilst retaining track position.  Nothing can really be done about this for 2015 as the difference in time between the two compounds just isn't large enough.  However, Pirelli will surely be evaluating the situation and is one of the prime reasons the teams want free choice on tyre compounds, giving those who can't make the tyres last an offset that works for them with one additional stop.

Returning to the 40 lap prediction we must also remember that this is based on the guidelines set forth by the supplier and since the 2013 debacle enforced by the FIA.  This covers but is not limited to minimum/maximum pressures, camber settings and tyres to be mounted in the correct orientation.  Tyres are an area that can offer a huge performance advantage over a rival and so it's obvious that the teams will run close to the margins to achieve the best performance, in doing so AND trying to increase tyre longevity you'll clearly run into issues.  The 40 lap prediction can therefore only be seen as a best case scenario, not a target to be aimed at.  Furthermore, given the simulation work used to predict this lifespan it's clearly void by the mere fact that the track was changed.  Sebastian's excursions outside of those limits aside the stint length would clearly be less than the 40 laps quoted by Paul Hembery, owing to the extra load going through the tyres at Radillion and their consequential deformation as speeds were increased down Kemmel straight.

Just as the teams were culpable for the problems we saw in 2013, I think in this instance the same can be said for Sebastian Vettel and his approach to the race.  No-one wants to see a failure, however, when you continuously push something beyond its tolerances it is bound to fail.  I just hope that everyone see's sense this time around, rather than chase Pirelli around with pitchforks insisting they change something.

EDIT 28/08/15 - Vettel aside here is a slideshow of other drivers etiquete through Eau Rouge and over Raidillon, of which Perez and Kvyat are the worst offenders - Slideshow

Furthermore, it would seem although others clearly took the short cut at Radillion the effects on the rear tyre were not as severe as those already highlighted on Vettel's SF15-T, most likely due to how rigid or softly sprung each car is.  In the example below of when Maldonado runs wide during FP3 his right rear unloads, coming down without such a sharp deformation and/or twisting force on the tyre.  Now we don't have speeds to see if they are travelling through there at similar velocities but we can see that post kerb hop the car is unsettled so much that the front wing collides with ground, suggesting a very different damping arrangement than the Ferrari.





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20 comments:

  1. I think this is a more than fair assessment. Its sad the level of flack that Pirelli continuous to receive from the sport when theyve built what the governing body had requested of them. Vettel for his part needs to review his mid race trips into the parking lot before he continues on this line of having done no wrong.

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  2. The question is just why shouldn't a tyre not stand such stress? As someone who worked on FEM simulations of tyres (not in the F1 field, and not an argument of authority (!)) The article lacks an explenation why what Vettel did is supposed to reduce the lifetime of the tyres in such a massive way (the 40laps statement is fact).

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    1. He/Ferrari reduced the lifespan of the tyre by 12 laps (just over a third) I think by the nature of the abuse I have levelled (cutting Radillion at high speed and unloading the tyre before battering it against the sharp edge of the kerb it shouldnt hit) it could be responsible for some of that loss of life. Furthermore we return to the 40 lap argument, Hembery said 'around' 40 laps, that could mean 38-42 given that he'd have likely said 35 or 45 if that were closer to the truth.
      He also infers as I have, perhaps I should have been more aggressive, that both the conditions (track temps) and the way the teams are using the tyres could have an impact on longevity.

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    2. Well, that are a little too many assumptions for my taste.

      But I'm really surprised that we are really at the point that tyre deformation (something that tyres are supposed to do for all kind of reasons like increasing the contact surface etc.) kills the tyres.

      Tyre deformation isn't bad per se (espencially in a F1 world where all factors and settings around the tyres are controlled by Pirelli) and not unique to Vettel and/or Spa.

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    3. I'm not saying deformations are bad, what I'm saying is that inconsistent deformations, with high wheel spin due to unloading and then further deformations to the tyres shoulder whilst at a peak temperature are clearly going to take a toll.

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    4. Well, it was obvious not that bad enough that Pirelli used that kind of deformations as explenation for Vettel's accident.

      Especially such blow-outs would happen at the point of the largest deformation/stress on the trye and not several hundred meters after it.

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  3. Brave to take on the insane and fiercely loyal prancing pony fans, Matt :)

    I'm glad to see somebody call BS on the off track.

    I think Seb's and Nico's failures are different, and would be interested to see if Rosberg did indeed go off track like that a bit.

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  4. Almost everyone on every lap cut the corner coming out of Radillion.

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    1. yeah but most of the had a 2 stopper not 1

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  5. Good article, Matt. Great pictures. The deformation around the wheel rim and in the side wall are indications of almost instantaneous high stress loading that are really hard to predict. The problem is that Pirelli are tasked with making the supposed race into something interesting. This is NOT racing - it is an invisible, somewhat unpredictable degradation of the tires that determines the outcome. What is needed are tires that allow maximum racing and then MUST be changed after a set number of laps. Let them go flat out racing without a tire degradation lottery!

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  6. Shut the fuck up

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    1. Wow really, it's just an alternate opinion, people like you should take a hike and have a big cry if you don't agree with the article. Pathetic.

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  7. I wholeheartedly disagree that tyre degradation has no place in the sport. As the race goes on I'm always watching the delta in tyres and thinking when would be best to come in pit. Additionally the variation in grip and tyre life by manufacturer and track temperature makes the strategy behind it that much greater.

    Without it Mercedes would be running at full trot unrestricted and uncatchable by Ferrari in most any scenario. At least now they (Mercedes)have to worry a little bit more if track temps go above what their cars are comfortable with.

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  8. With the differential nearly locked or at worst in limited slip mode there shouldn't be that much over speed on the unloaded wheel or all drive would be lost the loaded wheel as you would see on a road car.Therefore when the wheel hits Terra Firma having been airborne there shouldn't be too much of a problem.

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  9. That`s a lot of effort on building a case against Vettel.
    But its all useless because the fact is that Pirelli gave indications that the tires would be good for ~ 40 laps... which is 40 racing laps (this is important here) and that includes abusing them tires in the kerbs too.
    I`m pretty sure that 40laps expectancy wasnt based on cruising slowly with Safety Car speed, if Vettel had gone cruising on SC speed he could have managed even 100 laps.

    And if anything, the track temperature as it was, should have helped prolong that estimated 40laps with 1 set of tires, well into 50laps.
    As evidenced by the fact that Vettel had enough tread, traction and speed left in his tires to keep RoGro behind and lap even faster than some cars between 5 - 8 place that had fresher tires. Also:
    1. Vettel's three other tyres were in good shape and had no excessive wear
    2. The front left would be the tyre that wears out first around Spa

    I`m not disputing the fact that Vettel stressed his tires, but Pirelli already knew how everybody would race with them tires over the kerbs from the qualifying a day earlier, and their provision of 40 racing laps proved totally wrong. And their engineer at the Ferrari garage didnt object at the 1 stop strategy so the fault lies firmly with Pirelli and Pirelli alone.

    Do you really think that Pirelli was totally unaware of the technicalities you mentioned above before they gave their indications that the tires would be good for ~40 laps? If YES, then they are clearly employing the wrong people.

    Now this is probably what Vettel had in mind when he said that he wouldnt be standing that had the tire exploded 100 meters earlier: https://www.youtube.com/watch?feature=player_embedded&v=nyIQNM-1hUc

    Look at the incident above and you`ll realize that Vettel is totally justified to be so upset at Pirelli.
    As Mark Webber said... the irony of it all is that, had Vettel completed those last 12km Pirelli would have come out, saying ‘look how fantastic our tyres are’.

    Again a quote from Webber (very unlikely source to come out on Seb`s support):
    "Seb is one hundred percent right,” the Australian told Auto Motor and Sport. “You get slower, okay, but as a driver you must be able to rely on the fact that the tyre stays intact.”

    http://thejudge13.com/2015/08/29/the-tj13-news-saturday-august-29th-2015/

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  10. I think here we are missing something fundamental.
    For the sake of safety, its unnacceptable that the wear life of the tyre is te same as the fatigue life for its structure.
    If there is a safety margin between those two, Seb would have suffered a high increase on lap time and reduction of grip forcing him to change tyres without risking an structural faillure.

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  11. I see that you claim that Vettel's tire failure was caused by him going off track, but then you present the images of Radillon, explaining the forces that affect the tire, but not why they caused the failure. You just showed us how the tire reacts in Radillon, nothing more. While the right rear is loaded going through the left hander at the top of the hill, notice that it is on the side of the kerb closest to the white line - i.e. the lowest and least severe part of the kerb. Vettel doesn't even drop the tire over the edge of the kerb, which could potentially cause a puncture.
    In addition, you also show pictures of Vettel running wide at Stavelot and Malmedy, two right handers. This is where the left tires are loaded, and he runs them over the edge of the kerbs, so why didn't they fail first?
    I know it makes the most sense for a left hand tire failure since they take the majority of the punishment at Spa, so when the right rear fails, we assume something else must have occurred for that to happen. However, you haven't proven conclusively that Vettel's tire failure was related to his abuse of track limits. What I see here is Pirelli failing to build a race tire that can withstand multiple trips trough Eau Rouge and Radillon.

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    1. Firstly, I showed pictures of Stavelot and Malmedy as support that I refute Vettels claims that he did not run off the circuit, even if we delete Raidillion from the record.

      Secondly, I don't have the data or evidence to support what caused the failure I'm simply pointing out (once again) that being off the circuit, this time at Raidillion, is loading the tyre in a none linear way.

      I'm not trying to be conclusive with the article, just pointing out that sometimes it's easy to point the finger and blame one party when in fact it can take multiple conditions to unfold in order for a failure to incur.

      I do agree that from the outside looking in this does look like a poor job from Pirelli, I just feel there is more to this than has been made out...

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  12. I am absolutely no Vettel or Ferrari Fanboy, in fact I pretty much hate Vettel and have never been a Ferrari fan. But Tyres should simply not fail in this explosive way, regardless of the cause (within reasonably good reason of course). Ever since I have watched F1 I don't recall a tyre exploding unpredictably without a real reason. Sure there have been the odd spectacular failure Mansell etc but they all had a reason: cut by front wing endplate etc. The vast majority resulted in manageable deflations. Going over a kerb should never result in a tyre explosion, and failure due to wear?? What are people on?? The tyre should be un-drivable due to wear and not fail like this. Previous manufacturers managed it- Hamilton in China 2007 was it? He was going round far longer than he should have been and was on the canvas, the tyre did not explode, Schumacher regularly did the same. For me I don't even understand why there's a debate, it should never happen like it does in this F1 Era not in 2015. Surely it’s possible to make quickly degrading tyres without such weak structural integrity? If that's what you want of course, for me I'd like to see the FIA stop banning things that actually make cornering closer together possible, Blown floor for example, but that's a rant for another day!

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  13. Might have missed it but if we move Vettels Car one car width to the right, then wouldn't the left hand tyre be getting the same/similar abuse, but not be in any way considered breaching track limits or out of the ordinary ?

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Whilst I'm trying to keep atop of the blog you may have noticed of late that there is less content appearing. For those of you that haven't realised, most of my work has now been moved over to Motorsport.com where I'm working with Giorgio Piola.

I'm still doing the technical image gallery for each GP with the continued support of friend of the site Sutton Images. However, as always my time is limited and so this might not be updated as quickly as it once was, so keep checking back.

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