Bugatti has revealed that the tyres worn by the Chiron prototype during its recent record-breaking top speed run were “slightly modified”.

In August, the French firm became the first manufacturer to break the 300 mph barrier, with a "near-production" prototype of the Chiron clocking 490,484 km/h at Ehra-Lessien in Germany. The company has since “withdrawn” from the so-called speed wars.

Stefan Ellrott, Bugatti’s head of development, told whichcar.com.au the company worked with tyre supplier Michelin to modify the Pilot Sport Cup 2 rubber in order to ensure it survived such high speeds.

“We had to modify slightly the series tyre of the Chiron. It is still the series tyre, but with an additional layer of carbon-fibre in it,” Ellrott said.

“It is a very close relationship between Michelin and Bugatti, because Michelin is the only supplier of tyres for the Chiron, so we are together,” he told the Australian publication.

“What we did, together with Michelin, to make sure that there would be no risk with the tyres, was a lot of bench testing.

“We used a plane test bench in Charlotte [in the United States] to make sure that the tyre will be okay with more than 500 km/h,” Ellrott said.

“After that you might see that 500 km/h is okay, so you go faster and faster [with the tyre], so we could see what the fade would be.”