McLaren: Adjustable Front Brake Ducts

This year McLaren have had the option to alter rear brake cooling during the pit stops in a race. As a result they can vary brake temperatures and potentially alter tyre temperature slightly. This latter effect being possible from the heat conducting from the red hot brake discs through the wheel and into the tyre. This system has been used at various races and each driver appears to have preference when to use it. This system has been especially useful this year, as the tyres dropping below their operating temperature window will see grip their levels fall dramatically. At the British GP one of the mechanical updates McLaren have brought, is the front brakes now also have this adjustability.

The front brake duct appears to use the same mechanism as the rear. A flap opens up to uncover the brake disc, this allows more heat to pass out of the outer brake drum. To accomplish this, a small telescopic adjuster is fitted to the outer drum to move the flap.

Images taken over the Friday practice sessions also showed the mechanism hanging loose from the duct assembly. These images show the mechanism has a hydraulic fluid line and a bleed nipple, providing the surprising proof that the mechanism is hydraulic. As explained in the previous rear brake duct post, the ducts are altered centrally from an adjuster near the fuel filler flap.

It was previously presumed to be a cable operated system, using hydraulics may make the packaging of the system easier, as you don’t need to find smooth routes through the car for a bowden cable.

It’s also likely that this is a separate hydraulic circuit for this purpose, rather than a part of the cars high pressure electro-hydraulic system or the cars brake circuit. Using hydraulics over a cable is not a legal issue, as long as the system is operated when the car is at a stand still, then the adjustment mechanism is not an issue.

Now having front and rear adjustment to brake cooling , McLaren will be able to react to brake temperature issues, play with KERS harvesting without fear of overheating brakes and also alter the tyre temperatures front or rear, allowing for a better balance to be found during the race. With the weather expected to be mixed this weekend having this option will be extremely useful for the Race Engineers.

8 thoughts on “McLaren: Adjustable Front Brake Ducts

  1. This may be presumptive, but is it possible McLaren is using a thermally expansive fluid in the hydraulic line? It would be very difficult to police, but basically the idea would be that as the brake temperature heats up, the line heats up as well and opens the brake flap, and as it cools, the line cools down closing the brake flap. This would be illegal, but as I said, difficult to police.

    Presumably this could be accomplished mechanically as well, using materials with different CTE’s, but maybe the high CTE required to make this system effective would not have enough strength if done mechanically.

    • That seems like a great idea to control brake and tire temp (once designed/setup correctly – not sure how much the fluid heats from looking at that photo…maybe that metal pin at the end though). I don’t see how that would be legal (at least the idea of the rules) with respect to movable aerodynamics though. Hard to police; you’d have to prove that the ducts were moving then you could launch a complaint (good luck seeing that on camera).

      • I’ve seen ideas like this before when talking about these ducts, but as far as I understand it, these ideas miss the point of the system in the first place. The point is not to react to too much or too little heat in the brake disc, but rather to manually change how much of that heat is transmitted to the wheel. If this system self adjusted, you wouldn’t get the manual control over the heat transfer that you want to have.

        Correct me if I’ve missed the point myself, scarbs.

    • Yeah I get the feeling that if the driver is struggling to get a certain tyre into its ideal operating temperature, then adjusting the duct cooling would allow for a slightly higher brake temp and radiate heat out into the tyre. Possibly aiding in reaching this tyre window.

      The same could be applied if the brake cooling was insufficient and the disc/calliper got too hot, it could be opened up allowing more cooling. And for a tyre that was too hot also.

  2. But if it is done by temp, that could make an imbalance since not both front tires will reach the same temp, and one system could operate before the other side. Then an imbalance on tire temp and tire wear will be achieved. I’m not very technical just because I like it I follow, so I might be way off here. Just a thought though.

    • Yes, the gold slotted pick up for the track rod does alter the elements angle-of-attack, with steering. Other teams manage this at the steering rack end, although I have one of two teams with a similar solution.
      As is evident, the spherical joint housing on the track rod end has pins protruding from it. These ride in the slots in the gold clevis, such that the angle of the slot changes the angle of the track rod with steering movement.

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