McLaren’s new adjustable rear brake ducts

A new technological development from the Woking-based team has been the adjustable rear brake ducts which help in controlling the brake temperature as well as the tyre temperature as and when required. The diameter of the brake duct is 278 mm and the diameter of the wheel is 305 mm, hence the gap between the two is very less, thus heat released from the brake ducts automatically reaches the tyres.

During previous years, the teams tried to prevent the heat from the brake ducts reaching the tyres but now McLaren with the help of its innovative solution is able to use that energy to their benefits.

The conventional solution for brake cooling is to exits the brake flow from the outer face of the brake ducts. What McLaren have done is that they are exiting the heat from the brakes from the outer surface of the brake drum, and the outer face of the duct has been closed off from the disc. The advantage of this configuration is that now the heat passes in between the duct and the wheel, thus allowing more contact with the wheels.

conventional spoke configuration

MP4-27 spoke configuration

The other significant advantage comes from the difference shown in the two figures. The second image has 29 smaller extra drillings apart from the main 10 drillings. This is required because the heat is now exiting above the outer face of the duct(in front of which the 10 larger drillings are present). Also this allows more contact area for the spokes to absorb heat coming from the brakes, thus enhancing the amount of heat flow to the wheel.

In most cases, the cooling of the brakes is controlled by making changes to the inlet, especially to the cross-section to the inlet by taping or some other methods. But in case of the MP4-27, the inlet has not undergone any change, instead the team has introduced a threaded adjuster which in turn operates a flap. This flap’s function is to control the amount of heat released from the brakes by closing or opening the heat outlet on the outer surface of the drum.

Experts say that the brake ducts can be adjusted from a point near the flap where fuel enters the car. So, there might be a wire attached to the threaded adjuster and a mechanic can do the required adjustment very easily and quickly during the pit stops when even fractions of a second are of prime importance.

The technical regulations allow changes to the brake duct after the start of a race(during the pit-stops) and not considered to be a movable aerodynamic device(a movable or driver operable aero device cannot be present on the car according to Article 3.15 of FIA Technical Regulations). But the regulations also state that no adjustment to the brake ducts is allowed during the qualifying sessions or when the car is in Parc Ferme.

When the above-mentioned flap opens the cooling opening, then the brakes become cooler and the tyres gain temperature – this can be advantageous in cooler conditions when a driver is struggling to get his tyre up to temperature. The reverse can be helpful by heating the brakes and making the tyres relatively cooler and provide relief to the driver during heat-related degradation of tyres.

Apart from McLaren, this kind of system has not been seen on any other car this season; so it seems that the rival teams are able to operate the tyres in the temperature window similar to McLaren, if not better, using a more conventional brake cooling system.