Formula 1's teams have been told by the FIA that they cannot run trick brake systems that react to temperature to improve cooling during races, following a complaint by Red Bull.
AUTOSPORT can reveal that Red Bull wrote to motor racing's governing body ahead of the Abu Dhabi Grand Prix to seek clarification on the use of thermal energy devices within the air duct of the brake system.
The team contended that attempts to use either a bimetallic strip - which would change shape to open and close off cooling ducts depending on the temperature of the brake friction material - or a thermal actuator was a breach of the regulations.
In the letter, a copy of which has been seen by AUTOSPORT, Red Bull argued: "Use of such technology via either of the examples offered or similar devices will change the brake system, thus including the air duct, and are not reacting to the driver's direct physical input and are not under his complete control at all times as required by Article 11.1.4 [of the F1 technical regulations].
"RBR therefore contend such systems are in breach of the 2012 F1 Technical Regulations and seek your opinion on the matter."
Article 11.1.4 of the regulations states: "Any change to, or modulation of, the brake system whilst the car is moving must be made by the driver's direct physical input, may not be pre-set and must be under his complete control at all times."
The FIA duly responded to Red Bull on Friday confirming that it agreed with its view that the use of such systems would be a breach of the rules.
In a letter that was forwarded to all teams and seen by AUTOSPORT, the FIA's Charlie Whiting said: "In our view movement of a bimetallic strip and thermal actuator within the air duct as you describe would not be made by the driver's direct physical input, hence we believe such a system would contravene Article 11.1.4 of the F1 Technical Regulations."
AUTOSPORT understands that Red Bull's complaint was made after suspicions that at least one of its rival teams was using the concept on its car.
However, high levels sources at Red Bull's main rivals insist that they have never used the concept and agree that doing so would be a breach of the rules.
Red Bull's dialogue with the FIA shows how focused the outfit is on ensuring that it maintains every possible competitive advantage as it makes a push to win its third consecutive championship double.