IS THIS McLAREN’S COOL SECRET?

Auto Action’s regular columnist Chris Lambden has taken a deep dive into the possible technical breakthrough that is delivering McLaren Formula 1 domination.

ONE OF the fascinations around F1 is the technical breakthroughs which have re-defined the sport – or elements of it – for decades. The first rear-engined car; the first (Lotus 25) monocoque; the first carbon-fibre F1 car; ground-effect aerodynamics, rear diffusers, and so on.

The big technical discussion point around F1 at the moment centres around what appears to be the McLaren cars’ ability to ‘look after’ their tyres further into a race, or a stint, than the opposition.

That Oscar and Lando were able to put some 30 seconds on the field in the second half of the race at Miami was a huge crushing and leaves the opposition clutching at straws to try and figure it out.

Most notably, Red Bull team principal Christian Horner has been making fairly bizarre suggestions that McLaren has some form of water-injection to keep the rear tyres cooler for longer – and weren’t we all amused with the stickering on Zak Brown’s water bottle at Miami.

‘Tire Water!’

Not a lot of love lost between those two. …

Oscar Piastri driving the McLaren MCL39 Mercedes on on his way to a win in the F1 Grand Prix of Miami on May 04, 2025 in Miami-Photo by James Sutton/LAT Images

More recently, Red Bull has been targetting the McLarens with thermal imaging cameras and is convinced that the results show ‘blue spots’ which suggest that the McLaren brake drums/shrouds (see image in the latest issue of Auto Action digital – F1 News) are much cooler compared to others. That would in turn reduce the amount of heat being radiated from the brakes, via the wheel rims, to the tyres and stop them from overheating.

It also seems to explain the fact that, on qualifying ‘Softs’ the McLaren generally maintains its tyre performance over the latter stages of the hot lap – setting some very fast Sector 3 times.

But how? No, not water-cooling Christian …

There’s an interesting theory emanating from a YouTube channel, B Sport, in which an engineer with in-depth metallurgy knowledge puts forward a very interesting theory.

The key words are ‘phase-changing materials’.

This in itself isn’t a radical new thing. The simplest example in day-to-day life of a phase-changing material (PCM) is the ice cube you put in your drink. In the process of turning from solid to liquid (water) heat energy is absorbed and your drink cools – for as long as there’s enough ice to melt. Want it cooler for longer? Add another ice cube!

That’s all well and good, but what if you need to keep your drink cool for 45 minutes (the length of a Grand Prix stint)? You wouldn’t have enough ice cubes – but what if there was an external means of re-cooling the cube ‘on the run’?

F1 brakes, and the outer drums that enclose them these days are highly regulated. And, as our engineer points out, McLaren has no problems exposing the internals of its braking system when the drums are off and the car up on its stands in the pits. All pretty standard stuff.

But, he says, no-one gets to see the internals of the outer drums themselves. What if the drums were lined with a specific and undoubtedly very special phase-changing material or materials that operated in that way – effectively absorbing heat as its state was changing (under braking), keeping heat radiated to the tyres down – but then ‘reversing’ the process as the car ran down the next straight, with air re-cooling and phase-changing the material backwards to do the same job at the next braking zone?

The rear brake system on McLaren Formula 1 car has been the subject of much interest.

Wow! I’m fairly basic mechanically, but it’s possible to understand all that – assuming that there’s some space-age material that would behave in that way between the temperatures you wanted.

Obviously, the last thing you want to do is slow up the tyre reaching its optimum temperature quickly at the start of a stint or qualifying lap, so the material can only start to have its effect once that temperature is reached (see graph, left).

If our engineer is correct, it’s legal as far as the F1 regulations go – there’s no moving parts, aerodynamic or otherwise … it’s simply the use and placement of materials.

If this is being discussed on an online forum, then you can only assume that the other teams are flat out-sourcing metallurgy experts as we speak! 

I have no idea whether this theory is right or wrong, but it’s fascinating. Certainly, the concept of phase-changing materials is not new – it’s used very simply in household insulation material; more scientifically, it’s apparently used for ‘vortex generators’ (which improve aerodynamic performance, especially at slow speeds) on aircraft – at altitude (at –50C), the vortex generators retract, but re-deploy when things warm up as the plane descends for final approach and landing. In this case, material that softens, becomes elastic, but doesn’t liquefy, is the answer …

Is that what McLaren is doing – in its case using materials that absorb significant heat energy then cool quickly, back to its initial form, with the air flow generated by an F1 car at high speed?

I have no idea! But if so, someone has very cleverly thought of a way of utilising a science that’s been around for a while … and found, or developed, the right material, or materials, to do it. Wow …

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