Red Bull were forced to change their wheel hubs ahead of Saturday's final practice after questions over their legality.
According to Sky Sports, FIA technical director Charlie Whiting ruled that the wheel hubs gave the Red Bull an 'aerodynamic advantage' while also providing cooling for the brakes.
Article 3.15 in the Formula 1 Technical Regulations states "any specific part of the car influencing its aerodynamic performance" must be "rigidly secured to the entirely sprung part of the car" and must remain "immobile in relation to the sprung part of the car."
As such, Whiting declared them illegal, forcing Red Bull to make changes which involved them blocking holes in the hub from the inside.
This latest spate of questions about Red Bull's RB8 comes just a week after the hole in their car's floor was declared illegal in the wake of Mark Webber's Monaco triumph.