Explained: How new FIA ruling could impact McLaren's genius trick

Just prior to the Emilia Romagna Grand Prix, the FIA issued two technical directives to the F1 teams. 

One of these concerned the materials of the skid-block fixing points under the car, but it is nothing particularly invasive or which requires major changes.

The more interesting one was the second TD which covered what is allowed in brake cooling, after Red Bull raised a question with the FIA. 

As RacingNews365 revealed prior to Imola, McLaren has developed an intelligent cooling system in the brake drums, using something known as PCM or Phase Changing Materials.

It allows the team to control the temperature in the brake drum and avoid heat generated under braking from being transferred to the tyres, thus bringing tyre temperatures down. 

The TD, released on May 12th, specifies that materials which modify the internal volume of the cooling channels inside the brakes cannot be used as the air which passes through varies in temperature.

In essence, if there were an expansion or reduction of the section within the drum, it would contravene the rules which prohibit the use of active aerodynamic parts.

Based on the TD, it is correct to consider the response of McLaren boss Andrea Stella who believes the performance of the MCL39 has not been affected by the new directive. 

It is nevertheless important that the FIA felt it necessary to clarify what is and what is not acceptable when it comes to managing tyre and brake temperatures.