Tyre warmer ban and 18-inch wheels in 2021 Formula 1 package

Front tyres will also be narrower, dropping by 35mm to 270mm. The rears will stay the same, at 405mm, while diameters will increased from the current 670m to "700-720mm."

The next single-supplier contract will cover the four seasons from 2020-23, the first of which will be run with current tyre sizes and blankets.

That means if anyone other than Pirelli wins the bid they will have to develop tyres from scratch that will be used for only one year before the major package of rule changes comes on stream in 2021.

The loss of tyre blankets will be one of the biggest technical challenges that the winning bidder will face. The subject has been discussed many times over the years, but always dismissed.

The FIA notes that "tyres should provide safe performance when leaving the pits cold. The glass transition temperature must be chosen so that the tyres are never in a 'glassy state' when either the ambient or the track temperature is above 10 degrees centigrade."

It also adds that "for winter testing a specific low temperature tyre will be required. This will form the bulk of supply to the teams for European winter testing with a limited number of race compounds available," while confirming that "wet and intermediate tyres should also be capable of running without the need for pre-heating."

The FIA makes it clear that the "improvement of the show" is a the number one priority, and that the process should start with the final year of the current tyre sizes: "The provider should commit to achieving this in 75% of circuits in 2020, and to improve their performance with respect to this objective throughout the whole period of the tyre supply."

In addition, "in order to stabilise at a pressure that provides peak performance, the tyres must be capable of commencing running at cold pressures compatible with achieving suitable stabilised pressures."

There will be three compounds at each race, as expected with the simplified hard, medium and soft names. The FIA characterises the tyres as follows:

- Hard compound: 2s degradation achieved at 22% race distance Base lap time

- Medium compound: 2s degradation achieved at 18% race distance 1.2s/lap quicker than Hard compound

- Soft compound: 2s degradation achieved at 10% race distance 2.2s/lap quicker than Hard compound

The FIA hopes that there will be more strategic variety, saying that "the intent is to create the maximum number of race strategies yielding race times such that multi-stop strategies provide just enough potential of a beneficial outcome to encourage the greatest variety in the racing spectacle."

It says tyre wear is "considered desirable both for its impact on race strategies and to ensure tyres are not run to a point of excessive wear. A non-linear performance gradient change ('cliff') at a certain percentage of tyre wear would achieve this. It is suggested that an underlayer of low performance is designed below the tread compound to achieve this."

The FIA also wants tyres that can recover, saying "it is expected that aggressive driving or close following will incur higher tyre degradation per lap than gentle driving or driving in free air.

"Once a period of aggressive driving or close following ceases, the tyre should rapidly recover the lower level of degradation per lap associated with the more benign conditions."

The tender document also requests that tyre performance at the new size is "at least as good as the 2019 tyres".

Suppliers have until August 31 to submit their bids. A decision on technical and safety compliance will be made by September 14, and then afterwards the commercial aspects of any 'approved bidders' will be considered. Liberty will then make its choice, which it has to propose prior to official approval by the FIA.