Pirelli’s full report on the Silverstone debacle

Pirelli has tonight issued the following statement on what happened at Silverstone – and what the company plans to do next. See previous story for a summary.

After exhaustive analysis of the tyres used at Silverstone, Pirelli has concluded that the causes of the failures were principally down to a combination of the following factors:

 1) Rear tyres that were mounted the wrong way round: in other words, the right hand tyre being placed where the left hand one should be and vice versa, on the cars that suffered failures. The tyres supplied this year have an asymmetric structure, which means that they are not designed to be interchangeable. The sidewalls are designed in such a way to deal with specific loads on the internal and external sides of the tyre. So swapping the tyres round has an effect on how they work in certain conditions. In particular, the external part is designed to cope with the very high loads that are generated while cornering at a circuit as demanding as Silverstone, with its rapid left-hand bends and some kerbs that are particularly aggressive.

2) The use of tyre pressures that were excessively low or in any case lower than those indicated by Pirelli. Under-inflating the tyres means that the tyre is subjected to more stressful working conditions.

3) The use of extreme camber angles.

4) Kerbing that was particularly aggressive on fast corners, such as that on turn four at Silverstone, which was the scene of most of the failures. Consequently it was the left-rear tyres that were affected.

The only problems that had come to light before Silverstone were to do with delamination, which was a completely different phenomenon. To stop these delaminations Pirelli found a solution by suggesting that the teams use the tyres that were tried out in Canada from Silverstone onwards. When this proposal was not accepted, Pirelli found another solution through laboratory testing, with a different bonding process to attach the tread to the carcass. So the problem of delamination has nothing at all to do with what was seen in Great Britain.

 Following the conclusions of this analysis, Pirelli would like to underline that:

1) Mounting the tyres the wrong way round is a practice that was nonetheless underestimated by everybody: above all Pirelli, which did not forbid this.

2) In the same way, under-inflation of the tyres and extreme camber settings, over which Pirelli has no control, are choices that can be dangerous under certain circumstances. Because of this, Pirelli has asked the FIA for these parameters will be a topic of accurate and future examinations. Pirelli has also asked for compliance with these rules to be checked by a dedicated delegate.

3) Pirelli would also like to underline that the 2013 tyre range does not compromise driver safety in any way if used in the correct manner, and that it meets all the safety standards requested by the FIA.

 The logical conclusion is that it is essential for tyres with the performance and technical sophistication of the 2013 range to be regulated and carefully controlled by Pirelli itself. In order to ensure the optimal functioning of the tyres, the Italian firm would need real-time data from the teams regarding fundamental parameters such as pressure, temperature and camber angles. While waiting for new regulations that would permit Pirelli access to this data, vital for the development and management of these state-of-the-art tyres, the following measures are proposed for the forthcoming grands prix, in agreement with the FIA, FOM, the teams and the drivers:

1) The use of the evolution of the current tyre that was tested in Canada (and proved to be completely reliable) for the German Grand Prix this weekend. This represents the best match for the technical characteristics of the Nurburgring circuit. In particular, the rear tyres that will be used at the German Grand Prix, which takes place on July 7, have a Kevlar construction that replaces the current steel structure and the re-introduction of the 2012 belt, to ensure maximum stability and roadholding. Given that these tyres are asymmetric as well, it will be strictly forbidden to swap them round. The front tyres, by contrast, will remain unaltered.

2) From the Hungarian Grand Prix onwards, the introduction of a new range of tyres. The new tyres will have a symmetrical structure, designed to guarantee maximum safety even without access to tyre data – which however is essential for the optimal function of the more sophisticated 2013 tyres. The tyres that will be used for the Hungarian Grand Prix onwards will combine the characteristics of the 2012 tyres with the performance of the 2013 compounds. Essentially, the new tyres will have a structure, construction and belt identical to that of 2012, which ensured maximum performance and safety. The compounds will be the same as those used throughout 2013, which guaranteed faster lap times and a wider working range. This new specification, as agreed with the FIA, will be tested on-track together with the teams and their 2013 cars at Silverstone from 17-19 July in a session with the race drivers during the young driver test. These tests will contribute to the definitive development of the new range of tyres, giving teams the opportunity to carry out the appropriate set-up work on their cars.

16 Comments

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16 responses to “Pirelli’s full report on the Silverstone debacle

  1. Greg

    Nice to see Pirelli basically throw the entire situation back into the laps of the teams and claim essentially no responsibility.

  2. petes

    Well there we go – Merc should be allowed to join the test

  3. GeorgeK

    I can’t believe the interior and exterior sidewall structures of the tires are remarkably different enough to cause the explosions we’ve seen, due to reversing the left/right wheels. Lateral loads will be similar on left and right hand turns, whether applied on the inside or outside of the tire.

    Same with camber and PSI choices. The tires have to operate within a reasonable range of cambers and pressures to produce the perfomance required. Extreme settings just wouldn’t work at all, so why would they cause failures??

    Reads like a dog ate my homework excuse.

    • I’m similarly confused why left-right swapping is clearly worse. Although the tire’s camber means forces pass through the tire differently when mounted on the other side.

      In terms of camber and PSI rangers, Pirelli presumably design the tire with ‘reasonable ranges’ in mind. Operating outside those ranges may be sub-optimal for the tire. It could be too tricky to adjust the design or test every eventuality so Pirelli prescribe the operating range. Not an unreasonable approach IMHO.

      Teams used extreme settings before (Red Bull, Spa, 2011). Pirelli clearly didn’t anticipate the failures or they would have enforced the operating ranges.

    • RobDin

      The way I read Pirelli’s statement is that It’s the combination of things that make it dangerous. Not one of the complaints towards the use of their tires alone could make a tire explode but if you combine them it becomes dangerous. When you swap the tires then because of the asymmetric tire design you accelerate the warm up time of the tires. The same goes with lowering the tire pressure and the camber settings. The camber has as an extra result that it changes the point on the tire where the tire is the hottest, it is moved outwards (and near the point where if you swapped the tires the hottest point on the tires is closer to the weaker side of the tire than the harder side). Add to that an high speed track and because of the high speed the tires have a lot energy in them tires and the tires have so much energy that they could explode. The combination of these things created a dangerous situation.

      • Stone the Crows

        Yes, quite. And in addition to your well stated points, drivng over curbs at high speeds can cause shock waves inside the tyre and if it is already stressed in away that runs counter to its design a failure is inevitable. I think people underestimate the dynamics that a race tyre is put through, and then to deliberately engineer them to degrade at a particular rate along with that is begging for trouble.

    • floodo1

      They didn’t word it very clearly but the key word is “asymmetrical”. They know that the loading at Silverstone is higher on one tire than the other so they make that tire slightly different compared to the other. THIS is why they don’t want teams swapping side to side.

  4. prez02

    If you just swap left and right tyres, then the outer wall is still on the outside, and the inner wall is still on the inside, the tyres are “only” rotating the wrong way round, “against” the tread if you like. You’d have to mount them the wrong way on the rim to have the inner side on the outside,but then the rotation direction would be correct again. Now I think I saw a picture here showing a Merc in Monaco where the arrow indication the correct rotation pointing in the wrong direction, meaning the outer wall is still on the outside.

    • Miguel

      You are correct.

    • Kevin Robinson

      You are correct if they simply put a right tire mounted on a right wheel on the left side. But are they taking a right tire and mounting it on a left wheel? If they do this, that would be a different inside and outside. Not sure which is true though…

      • Ryan

        Why would it matter if you you still had the outside of the tyre on the outside of the car? There is no tread on these tyres. Power goes to both wheels but I guess there or more right hand turns on an anti-clockwise track that might make a difference. I can understand putting the inside of the tire facing the outside somehow giving an advantage with camber correction and under inflation also somehow helping. That kerb in turn 4 at silverstone has an inch high cement lip that the left rear would hit as the car got all four back on the track to get to turn 5. I blame the teams for not following instuctions from the manufacturer. I know they are trying to squeeze every inch out of these cars but if the tyre is marked “left rear” you should put the tire there. If you don’t and they fail that’s on you. Apparently teams discovered this during winter testing and have been doing it through out the season. The teams moaning the most about changing the tires are the ones doing it because they know kevlar ones don’t have the advantage of running them on the wrong side of the car. Ferrari, Force India and McLaren and Merc have been playing around with swapping. With no rule against swapping I guess it’s technically legal but I think the loophole should be closed so that teams have to run the tires as designed.

  5. Sarah

    Does seem to be a case of passing the buck. We were lucky there weren’t more serious consequences on Sunday. It would seem wiser to work together to sort out the problems instead of the parties involved seeking to pin the blame anywhere but themselves.

  6. Catherine

    Anyway, don’t teams label their tyres anymore? They used to put tyre warmers on them with which wheel they were supposed to be put on. I know for sure Ferrari did, surely they weren’t the only team?

    • Greg

      Because the rear tyres this year have asymmetric tread, teams have been purposely switching the left rear with the right rear in order to gain some advantage. Adam wrote about this a few weeks back.

  7. Steve C

    So, Pirelli is saying that the right hand tires were placed on the left hand wheel and vice versa. Is this on purpose or by accident? And if it were by accident, wouldn’t the teams get about half correct (if the tires weren’t marked in any way to help the teams locate the right wheel with the right tire)? I guess we need a statistician

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