Second practice at the Formula 1 Japanese and United States Grands Prix will be extended by 30 minutes.

The one-hour session will increase to a more traditional 90 minutes as teams work with official tyre supplier Pirelli on refining next year’s rubber.

Strict limitations on in-season testing and a packed calendar have conspired to make tyre testing difficult, with a number of changes on the Italian rubber company’s wish list.

Among them are changes to the front tyres in an effort to dial out some of the understeer which has been prevalent this season.

“The plan is to test mainly compounds,” explained Mario Isola, Pirelli’s Head of F1 and Car Racing.

“We have the opportunity to use FP2, that will be 90 minutes and not 60,

“All the 20 cars will running different plans, as usual, they are blind, so teams are not going to know what they are testing.

“But that’s really important for us; it’s important to find new opportunities of testing because with such a busy calendar with the 24 races next year, it will be – I don’t want to say – almost impossible to find the space.

“The European season is shorter, to stay on track Tuesday and Wednesday after the race is difficult, and so we need to find new opportunities.

“The teams were very collaborative in finding solutions, and one solution is to test during free practice.”

Ironically, changes to the Formula 1 weekend schedule have seen traditionally 90-minute sessions trimmed back to an hour.

For teams, there is a competitive impact on the change, with increased wear on limited components such as power units, and gearboxes, not to mention the costs incurred in running the car for an extended period.

“I know it’s a big effort from them because they are fighting for the championship and they are going to lose one session,” Isola confessed.

“But it’s really important for us to provide a product next year that is even better compared to what we have this year.

“We are happy with the current product, but we know that teams are developing the cars; performances are increasing.

“We need to reduce a little bit the understeer, we need to fine-tune a couple of compounds,” he continued.

“And we need the final validation on track to be sure that we are going in the right direction to have even a better championship next year.”

Pirelli has worked to spread the load across all 10 teams, and 20 cars, in an effort to both minimise and equalise the impact the two sessions will have,

“We are planning to give them our run plans with a mileage that is similar to what they have during a normal FP2,” Isola explained.

“We will run the same number of laps with blind prototypes.

“As I said, we are trying not to change too much the construction during this test because they set up the car for this weekend, so it’s important that we don’t have a complete different construction and we [do not] oblige them to change too much the set-up of the car.

“So working with the teams, we’re trying to find [a] clever solution in order to give us the possibility to test and not disrupt too much the weekend for them.”

The Japanese Grand Prix on October 7-9 immediately follows this weekend’s Singapore event while the US Grand Prix is scheduled for October 21-23.