Williams reveals that an issue with a wheel nut retainer was the root cause of Robert Kubica's retirement from last Sunday's Russian Grand Prix.
The revelation follows a statement from Polish oil refiner, Orlen, which sponsors Kubica and the Williams team, and which yesterday issued a brief statement querying the exact cause of the Pole's retirement just 27 laps into the race, his first DNF of the season.
"In connection with the withdrawal of Robert Kubica from Sunday's race as part of the Russian Grand Prix, we have officially asked the ROKiT Williams Racing Team for clarification," read the statement.
"Based on that, we will take actions related to the enforcement of contractual obligations."
The move came amidst media speculation that the Pole was retired in a bid to either save engine mileage or due to a lack of spares at a time the sport heads into the final, long-haul phase of the season.
"We opted to retire Robert in order to conserve parts ahead of the intense flyaway races which end the season," explained senior race engineer, Dave Robson at the time. "It's a very disappointing way to end two weeks on the road."
However, clearly in reaction to Orlen's statement, Robson has given further insight.
"We found an issue with the wheel nut retainer on George's car," he said, according to Motorsport Week, "which led to the front-right wheel not sitting perfectly. This caused a lock-up under braking.
"The design is very mature and well-proven," he added, though the Grove outfit has history in terms of wheel nuts. "The remaining inventory will be inspected thoroughly, and we do not anticipate a repeat of the issue.
"Unfortunately, we were forced to retire Robert's car due to the amount of accident damage we sustained in the Singapore-Russia back-to-back races in order to protect ourselves going into the next events.
"The team has worked extremely hard to ensure race quantities have improved ahead of Japan and the final races."