Pirelli and the problem of ‘marbles’

In order to ensure the spectacle – and the uncertainty of races – Pirelli provides teams with tires that degrade, intentionally, more than the rubber provided by Bridgestone in recent years. However, the greater degradation of the tires also implies a significant increase in the deposit of rubber – the famous ‘marbles’ – on the track, which poses a problem for the drivers.

Thus, after his spectacular off-track excursion in Malaysia, Vitaly Petrov attributed part of the responsibility to these ‘marbles’ left by the drivers on the track, lap after lap: “To be honest, I still don’t know what happened,” the Russian told Autosport. “This corner is tricky but you don’t take all the risks there. There were two laps to go, I knew Lewis [Hamilton] was behind me and I knew the tires were still in good shape […]. I think I picked up some rubber and as soon as that happens, you suffer a bit of understeer.”

The cleanliness of the track is a fundamental factor for understanding and the smooth running of the race. It is for this reason that the FIA, with the drivers’ agreement, decided to reverse the location of the pole position on the starting grid at Sepang, as the left line, traditionally reserved for the pole-sitter, was dirty due to an excessive rubber deposit.

But more generally, simply driving off the racing line is a disadvantage known to all amateur or professional drivers, and the increase in rubber buildup off the line could worsen this phenomenon. Last February, Sebastian Vettel was already concerned: « Mid-race, there will be so much that the adjustable rear wing will be of no help, because when you’re off the line, you’ll have to brake earlier. »

Paul di Resta confirmed this hypothesis of the German driver after his race in Malaysia: « There were a lot of ‘marbles’, maybe too many. […] Towards the end of the race, it became difficult to overtake ».

But another problem emerged this weekend in Malaysia: « The other big problem is that in the middle of the turns, these pieces of rubber would hit my hands when I turned the steering wheel » explains the Force India driver. « Rubber is not the softest material, and if you get it in the right place, it can hurt. It happened to me several times this weekend, and when you enter a turn, the rubber rolls on the tires and is thrown into the air »

The remarks of the Scottish driver were indeed echoed by none other than Sebastian Vettel, the current championship leader: « A piece of rubber suddenly ended up in the middle of my visor. […] They’re like projectiles fired from the car in front of you. »

« Imagine Singapore or Monaco, where a fan could suddenly find a piece of gum in their tea » he worries about the spectators with his own sense of style.

Paul Hembery did not wish to comment before receiving more feedback from the drivers. Thus, even before Sebastian Vettel spoke on the subject, the Pirelli competition director stated: “I haven’t had any comments from the top three drivers, but if it’s really a problem, we’ll have to think about it,” Hembery commented before adding: “The ‘marbles’ have to go somewhere.”

Pirelli and F1 thus find themselves facing a dilemma, as creating more spectacle through programmed tire wear involves a significant increase in rubber deposits on the track, which could work against overtaking. “I don’t have a magic wand; I’ve been told it was the most exciting race in a long time. If there were no ‘marbles,’ would it be as exciting?” wonders Hembery.

It remains that if the problem doesn’t seem to be too serious yet, it could be different during the European season where Formula One will race after GP2 cars also equipped with these Pirelli tires. The buildup of ‘marbles’ could therefore be even more significant, and both Pirelli, the FIA, and the teams will need to consider solutions to address it.