During a three-day IRL test session at the Indianapolis Motor Speedway in April, a problem was encountered with the new track surface.
As a result of wear problems, tyre supplier, Firestone, withdrew its teams from the test after just two hours, in order that it could fully investigate the problem.
Subsequently, Firestone and its teams returned to the IMS, and the test was successful, problem solved.
It's worth noting that Firestone is sister company to Bridgestone, which did not encounter any problems at the IMS.
We also hear that Bridgestone had another tyre - good for another 0.2s a lap at the IMS - but this wasn't taken to the USA due to "potential durability issues".