F1 could switch to low-profile, 18-inch wheels by 2020.
That is the claim of Auto Motor und Sport, reporting that the change could come a year earlier than the revolutionary new car regulations being planned for 2021.
That's because Pirelli's contract runs out at the end of next year, with potential rival brands wanting to become the sole tyre supplier needing to lodge their interest this month.
18-inch wheels would match the "futuristic" image of F1 cars that Liberty Media wants for 2021.
"We once had product designers draw cars of the future," said Pat Symonds, who is heading the group that is coming up with the 2021 rules.
"I assume that in the end we will get something in the middle."
Pirelli looks set to be making plans of its own for 2019 as well, having acknowledged that the tyres this year could be improved for better racing.
"One of the problems is that the soft, supersoft and ultrasoft are very close together," Pirelli's Mario Isola admitted to Italy's Autosprint.
"For next year we are working on different compounds to have a bigger gap and create the famous crossover that allows you to have different strategies," he added.
Bahrain International Circuit - Winter testing