F1 teams braced for double jeopardy at 'uncertain' United States GP

The United States Grand Prix will feature a step change in the Pirelli tyre range, a measure introduced this F1 season by the Italian supplier.

It is the second time the F1's sole tyre manufacturer has implemented a gap in its range for a round during the campaign, following the Belgian Grand Prix in July.

However, poor weather at Spa-Francorchamps prevented teams — and Pirelli — from determining how a step would impact strategy.

Therefore, the trip to the Circuit of the Americas will be the first true test of the concept, which has been devised to shake up the strategic status quo.

In Austin, the C1 compound (the hardest of the six in the overall range) will be used in conjunction with the C3 and C4 varieties.

Last season, the hard tyre at COTA was the C2 compound. The medium and softs remain the same.

According to Pirelli: "The increased performance difference between the hardest compound and the middle one should, theoretically, give rise to two scenarios.

"If drivers prefer the C1, the slowest but also the most consistent of the three, then they could run a one-stop race combining it with the C3.

"On the other hand, using the latter along with the C4, with its improved resistance to degradation, would produce quicker lap times but would almost certainly require two stops."

Adding further jeopardy into the mix is that the United States Grand Prix is another sprint round, like in Belgium. This means teams will have only one hour of practice to run the different compounds.

"Another similarity with the Belgian round is that Austin is also running to the sprint format, which means teams only have one hour to try the various options over long and short runs, which could add to the uncertainty as to how the weekend might pan out," added Pirelli.

Last year, the one-stop strategy was the prime approach, with only a few cars opting for a planned two-stopper.