F1 uncovered: The hidden McLaren MCL39 brake design details

One of the big talking points during the opening phase of the season is going to be tyres with Pirelli’s F1 2025 offering giving the teams plenty to think about.

Their sensitivity to temperature has always been a crucial aspect of getting the most from the Italian manufacturer’s product and this season certainly is no exception.

F1 tech analysis: McLaren MCL 39

Now whilst you might only consider the role the driver plays in optimising those temperatures over the course of a lap or stint, in order to extract the best performance from them, the other ingredient that should demand your attention is the design of the brake assemblies.

And whilst their primary function is to cool the components housed within the assembly, including the discs and calipers, there’s also scope for the teams to alter the thermal interaction between the brake drum and the wheel rim, which in turn will have an effect on the bulk temperature of the tyre.

The game changed a little in this respect with this generation of cars as not only are teams no longer allowed to dump air and heat out of the wheel rims face and by extension of that improve the cars aerodynamic output, the size of wheel rim rose from 13” to 18”, increasing the size of the wheel well as a consequence.

The increased wheel diameter also resulted in the brake disc size being increased by around 50mm at the front of the car and around 10mm at the rear, resulting in the upright and caliper also needing to be redesigned to accommodate it.

As a consequence of the regulation changes the space within the brake drum assembly has increased substantially, to which the teams reacted accordingly, with the first step being the introduction of a fairing that envelopes the brake disc.

This enabled teams to refine how cool air was delivered to the brake disc, whilst also providing a means to route the heat being generated around the assembly in order that it interacted with the wheel rim in a more favourable way.

After their initial design layout failed to provide the desired results, McLaren quickly settled on a solution that they’d continued to cultivate over the course of the last few seasons.

On the left-hand side of the image, below, we have the disc and caliper fairings in place on last season’s MCL38.

On the right-hand side of the image we have the S-shaped cool air feed for the caliper in place, which is split into two tracts that feed both sides of the caliper more evenly, whilst more pipework is connected to the window created within the caliper fairing that allows heat generated by the disc an escape past the caliper and is then fed back around the loop.

The central part of the image is merely these two images overlaid in order to give you a better idea of how the ducting snakes around the assembly and the impact that might have on the cold air being introduced to the system and the heat being generated by the components.

And whilst McLaren already seemed to have a pretty decent handle on the tyres, they have made changes to their layout here this season in an effort to better manage the temperature relationship between the brake components and the wheel rim.

This should, in turn, aid in a more stable bulk temperature for the tyres and ultimately deliver more performance and better longevity from them.

The brake-drum assembly is made up of three main nests, with the MCL39’s arrangement seen below.

As you can see the team have made changes to their arrangement this season, casting aside the dual tract, S-shaped arrangement they’d come to use over the course of the last three seasons, favouring a more direct routing for the cool air to the caliper, via its fairing.

Meanwhile, the pipework connected to the caliper window has also been revised, which has allowed the team more space with which to design the secondary nest (centre).

Notably we can see this is much more like the designs from the previous generation of cars (below – McLaren MCL35M), with the heat and airflow on that level moved in between it and the void created by the outer drum.

Various channels and baffles can be seen on this nest as it’s important for the team that the heat is distributed to the right areas, in order that it has a corresponding effect on the wheel rim and subsequently the tyre.

Prior to the change in regulations, the airflow and heat could just be ejected out of the wheel face, whereas the teams are now required to have a sealed outer drum, which acts as the final nest (right), with the heat rejected out of an outlet on the other side of the end fence (inset, arrowed).

Whilst we’ve honed in on McLaren, as they’ve probably had the biggest change in approach across the span of this generation of car and they’re certainly the team that have made the most significant changes from last season to this, it’s not to say that other teams don’t value this in terms of development.

All of them have made significant strides throughout the course of this regulation set, with changes made at the start of each season and being optimised over the course of the campaign.

Furthermore, we’ve only focused on the front brake duct assembly here, whilst there’s also clearly development been occurring at the rear of the car too, albeit due to their size and lesser role in  controlling the tyres temperatures, with a more broader approach taken to ensuring that the heat that is generated is positioned correctly.

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