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After tires popped at Spa, Formula One and Pirelli instituted limits on tire pressures. The minimum allowed on any car at Monza was 19.5 psi. To enforce this, an FIA delegate measured left rear tire pressures on the four front cars on the grid and found that both Mercedes’ tires were below the minimum pressure.

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The end of Mercedes’ race was incredibly bizarre. Not only did Nico Rosberg’s old engine burst into flame with two laps to go, but Lewis Hamilton was told to increase his pace while he had already established a comfortable gap ahead of Sebastian Vettel for the win. “Don’t ask questions,” radioed over the team. “We’ll explain it after the race.”


The team was all quiet on what the potential problem may have been. Were they trying to establish enough of a gap to pit one more time? Was there a problem with the car itself?

Soon, the issue came out: Mercedes may have been running tires under Pirelli’s minimum recommended air pressure. It was very likely that Lewis was told to push to build up more heat in his tires, or to increase his gap in case of a time-based penalty for the tire snafu.


According to Fox Sports, all the teams had been given fair warning about the new tire pressure limits instituted after tires popped at the Belgian Grand Prix. Minimum pressures as wel as maximum blanket temperatures would be checked by the FIA for Pirelli.


The technical regulations regarding tires are as follows, and not incredibly specific:


Pirelli clearly added a minimum pressure for Monza as allowed under Rule 12.5.3: 19.5 psi. Slightly deflated tires allow more of the tire to come in contact with the track, as mentioned in the rule.

Violation of a technical regulation regarding a safety issue like this is serious business. Cars were recently disqualified from GP2 results for violating tire pressure rules there. Would F1 be just as harsh?


On the grid, with the tires out of their heat blankets, a FIA delegate measured the tire pressure of the left rear tires of the Ferrari and Mercedes cars under the guidance of Pirelli. Ferrari’s cars were fine, however, Lewis Hamilton’s tire was 0.3 psi low and Nico Rosberg’s was a whopping 1.1 psi under.

Team representatives for Lewis Hamilton and Nico Rosberg’s cars were summoned to the stewards after the race. Mercedes F1 executive director Paddy Lowe confirmed that they told the stewards everything that they had done with the tires.


It was a bizarre occurrence: if this was a safety matter, why weren’t the two Mercedes pulled in immediately? Was it not really that dangerous to be on underinflated tires? Was there some doubt as to the measurements that were taken?

A lengthy meeting after the race finally came to a conclusion: no penalty. Mercedes’ result stood as-is, and Lewis Hamilton gets to keep his 53-point championship lead on Rosberg.


“We need to talk about procedures in the future, but for the particular incident, there was no penalty,” explained Toto Wolff.

Wolff claimed that their tire pressures were at the minimum when the cars left the garage. Formula One backed up Wolff’s claim in their decision: when the tire pressures were taken by the team, they were legal.


Formula One’s statement on the matter explained the stewards’ findings:

In making this determination regarding the pressures, the Stewards noted that the tyre warming blankets had been disconnected from their power source, as is normal procedure, and the tyres were significantly below the maximum permitted tyre blanket temperature at the time of the FIA’s measurement on the grid, and at significantly different temperatures from other cars measured on the grid.


This explained the discrepancy in measurements. There are so many variables at play there: how long had the blankets been disconnected? Did Ferrari leave their blankets powered-on longer than Mercedes? Was one side of the track cooler than the other? How much air could have been unintentionally released when Mercedes took their own measurements?

Because tire pressures vary so much with temperature (among other factors), it was hard for some to believe that a hard and fast limit would be taken with the tires cold. Formula One’s stewards recommended that Pirelli work with the FIA to determine a more consistent method of checking tire pressures in the future so we’re not stuck debating underinflated rubbers like some other sport.


Mercedes, as tense as they were immediately following the race, can finally relax and celebrate Hamilton’s insanely dominant win, although I’m certain that this controversy has given life to a whole new breed of conspiracy theorists.

Luke Smith of NBC Sports joked about this being “Deflategate II,” so I think we’ll call them the Tireghazi.


Photo credit: Getty Images

Contact the author at stef.schrader@jalopnik.com.

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