Brake Ducts, Tire Cooling, and beyond

[AR3-GP]

Inspired by the Mclaren MCL-39, here is a place to discuss innovative approaches to tire cooling in Formula 1

Here is the video an interesting watch who knows how accurate or feasible it is,

[AR3-GP]

IF Rob Marshall is the master mind behind keeping these tyre temps under control and pitched his ideas to Red Bull ..

If that were the case, there would at least be the slightest idea of what is happening within or around those rears. I mean direction-wise.
That would be the base source of the tirewater circus, something that kinda acts like a mini-airco with thermostat.
Brilliant nonetheless ... hats off

I saw B Sport had a video which suggests use of bimetallic strips and reversal of airflow in the wheel hub assembly IIRC.

Here is the video an interesting watch who knows how accurate or feasible it is,

Maybe, maybe not, but it is an interesting an idea. This kind of “switching” system (or other implementations of it) would explain why the MCL-39 doesn’t have the compromises of the RB19 and the SF-24 which were bad qualifying cars because they didn’t heat the tires up quickly enough for 1 lap pace. The drivers had always complained over the radio about the tires being cold and there were media reports about it. This is the major difference I see to how the Mclaren operates.

I’m confused though because carbon fiber is not a good conductor of heat.

Here is the video an interesting watch who knows how accurate or feasible it is,

Maybe, maybe not, but it is an interesting an idea. This kind of “switching” system (or other implementations of it) would explain why the MCL-39 doesn’t have the compromises of the RB19 and the SF-24 which were bad qualifying cars because they didn’t heat the tires up quickly enough for 1 lap pace. The drivers had always complained over the radio about the tires being cold and there were media reports about it. This is the major difference I see to how the Mclaren operates.

I’m confused though because carbon fiber is not a good conductor of heat.

He mentioined in part 1 of the video where he didn't really go into details of his ideas Red Bull using thermal cameras on the drums of teams using pit stops. The McLarens were cooler than every other team. I'm aware of them using the thermal cameras this weekend but though it was monitoring the tyres themselves not the cake tin.


If that is true than its suggesting something is going on there. And seems he is talking from an area of expertise in phase changing materials.

Maybe, maybe not, but it is an interesting an idea. This kind of “switching” system (or other implementations of it) would explain why the MCL-39 doesn’t have the compromises of the RB19 and the SF-24 which were bad qualifying cars because they didn’t heat the tires up quickly enough for 1 lap pace. The drivers had always complained over the radio about the tires being cold and there were media reports about it. This is the major difference I see to how the Mclaren operates.

I’m confused though because carbon fiber is not a good conductor of heat.

He mentioined in part 1 of the video where he didn't really go into details of his ideas Red Bull using thermal cameras on the drums of teams using pit stops. The McLarens were cooler than every other team. I'm aware of them using the thermal cameras this weekend but though it was monitoring the tyres themselves not the cake tin.


If that is true than its suggesting something is going on there. And seems he is talking from an area of expertise in phase changing materials.

Upon further review, I stand corrected. Carbon fiber can in fact be made into a good thermal conductor by introducing additives and changing the fiber orientation. So it is possible to have a significant transfer of heat from the wheel rim, across the cake tin cover, and into the air which is exhausted from the brake tin. Turbulent air flows inside the cake tin layers would also increase the ability to transfer the heat from surface of the carbon tin into the airflow and out of the duct exits, while introducing additional drag.

As I’ve repeated, I’m convinced this is a connection to why Mclaren has no straight line speed with the DRS. They are regularly 6-7 km/h down on the others. This is a lot of energy at top speed. Some of it may be due to downforce, but not all of it. They had a much smaller rear wing than Red Bull. Their tire cooling measures consume flow energy and this is not affected by opening the DRS flap. I think that’s why they have been pursuing mini-drs, flexible wings, and so on to reduce drag. It was a stated priority of Stella in the pre-season.

Here is the video an interesting watch who knows how accurate or feasible it is,

Thnx, very interesting idea indeed !
I do agree with AR3-GP that the McL drag somehow feels to be a result/side effect.
I'm no aerodynamicist by any means, so can't say anything smart or clever on that. But still .. it's pretty noticable.
Thet extreme traction out of corners, you guys reckon that's related to better state of the tires .. or just PU grunt combined with overal good mechanical grip ?

If I were RB I'd hire the guy to elaborate a little bit more while getting rid of his studentdebt ..

Interesting idea. There is a thermal recovery time that needs to be considered with such a solution though. If you're frequently on the brakes and pumping heat into the system, the PCM will not have enough time to cool down and revert, and f1 carbon brakes can get really damn hot on peak loads. It feels like eventually, the continuos braking will render the PCM useless for it's intended purpose, essentially ending up with dead weight on the rear.

Also, do we know how much "freedom" there is to incorporate this on the inside of the cake tins?

If it turns out to be this, I really hope we learn more about how they made it work, because there are many challenges and limitations that one needs to navigate in order to feasibly use this as an "active" cooling solution.

Interesting idea. There is a thermal recovery time that needs to be considered with such a solution though. If you're frequently on the brakes and pumping heat into the system, the PCM will not have enough time to cool down and revert, and f1 carbon brakes can get really damn hot on peak loads. It feels like eventually, the continuos braking will render the PCM useless for it's intended purpose, essentially ending up with dead weight on the rear.

Also, do we know how much "freedom" there is to incorporate this on the inside of the cake tins?

If it turns out to be this, I really hope we learn more about how they made it work, because there are many challenges and limitations that one needs to navigate in order to feasibly use this as an "active" cooling solution.

Worthy of a split topic, but since we’re here, I’ll leave that to the mods…

I don’t think the system requires the switch to open and close repeatedly during a stint or from corner to corner. You would just want to start in a state with cold tires and cold brakes where brake disc heat is used to heat up the tires (fast tire warmup) and then once the tire is heated, you can switch to rim cooling mode (flow reversal). The thermal saturation would be desired because it would allow the system to stay in the rim cooling mode.

The brake duct inlet and outlet blanking would allow Mclaren to control the rim cooling “power” and thus the equilibrium tire temperature.

Also the rear brakes are much smaller than the front brakes, not only because brake bias is forwards, but also because of harvesting on the rear axle through the drive shaft. It reduces the amount of energy that the rear brake disc needs to dissipate as heat. You have this big wide 18” wheel rim at the rear, and considerably less energy actually being dissipated within compared to the fronts. It’s no wonder that someone thought this volume could be used to do something more innovative.

...... Carbon fiber can in fact be made into a good thermal conductor by introducing additives and changing the fiber orientation.

Not just good, pitch based ultra high modulus fibre can be an excellent conductor of heat, (much) better than e.g aluminium. With the caveat that it is directional.

https://www.ngfworld.com/en/fiber/high_ ... ivity.html

(So note that the 1200 W/mK is just the fibre, in fibre direction. Making a composite out of it will lower values a lot, but you can still exceed metals, and at much lower weight)

...... Carbon fiber can in fact be made into a good thermal conductor by introducing additives and changing the fiber orientation.

Not just good, pitch based ultra high modulus fibre can be an excellent conductor of heat, (much) better than e.g aluminium. With the caveat that it is directional.

https://www.ngfworld.com/en/fiber/high_ ... ivity.html

(So note that the 1200 W/mK is just the fibre, in fibre direction. Making a composite out of it will lower values a lot, but you can still exceed metals, and at much lower weight)

Great insight, thank you.

[AR3-GP]

““Just struggling a lot with the brakes again the whole weekend,” he said. “So, yeah, very inconsistent. That’s a bit of a problem.””


I’m wondering if Max’s “brake problems” in the last few weeks are not connected to Red Bull’s tire cooling experiments….

A few thoughts too, and hopefully he does a follow up video on phase change material he mentioned.

But thinking last year on RBR claims of water inside the tyre of the McLaren. This wouldn't play in with the phase change material would it. Obviously not as what ever material changing to water inside the brake drums, but in the comments someone mentions in its simples form ice melting solid to liquid feeling water cool, but part of this wouldn't be a side effect of what ever materials they are using could it.

A clever air circulation. Stella also denies that her exceptionally good tire management in the race has nothing to do with the problems that sometimes make it difficult for drivers to set the perfect lap in qualifying. "We don't pay a price per lap for caring for the tires better than others. It's no problem for us to get the tires into their working window quickly." In qualifying, drivers are more likely to complain about a lack of feel for the front axle.

The opinion is now gaining ground in the scene that the engineers in Woking have found a particularly clever solution for circulating air in the brake ventilation drums, keeping the brakes hot while keeping the tires cool. The external shape of the drums is standardized. Inside, you have complete freedom. You're not allowed to install any explicit cooling elements, but you're not restricted in the choice of materials.

An insider speculates: "Perhaps they circulate the air in such a way that it stays cool in the crucial areas and shield the heat through the use of certain materials." Chief Technical Officer Rob Marshall is said to be the father of the system. He has been carrying the concept around with him for years, but has only now made it work. That would be bitter for Red Bull. Marshall was at Red Bull for 17 years before moving to McLaren in early 2024.

Stella also made an interesting statement. "Even when it gets hot, our car stays cool. We've developed a very efficient cooling system." This also affects tire temperatures. If the car as a whole gets too hot, it radiates to the tires. Stella's statement also explains why the McLaren is near the back in terms of top speed. More cooling reduces efficiency.

https://www.auto-motor-und-sport.de/for ... peraturen/

We have hit the mark with these theories in my opinion.

An insider speculates: "Perhaps they circulate the air in such a way that it stays cool in the crucial areas and shield the heat through the use of certain materials.

@TimW, to your point about the heat transfer being anisotropic in the fibre, that could certainly create an opportunity for exploitation. Shield heat in some areas and transfer it in other areas based on the orientation of the fibres inside the resin.

It was written elsewhere, that it's something which carries over to 2026, so this is something that all teams must invest in and understand or they will be behind Mclaren in 2026.

I have requested that these post be moved to a separate thread.

Maybe, maybe not, but it is an interesting an idea. This kind of “switching” system (or other implementations of it) would explain why the MCL-39 doesn’t have the compromises of the RB19 and the SF-24 which were bad qualifying cars because they didn’t heat the tires up quickly enough for 1 lap pace. The drivers had always complained over the radio about the tires being cold and there were media reports about it. This is the major difference I see to how the Mclaren operates.

I’m confused though because carbon fiber is not a good conductor of heat.

He mentioined in part 1 of the video where he didn't really go into details of his ideas Red Bull using thermal cameras on the drums of teams using pit stops. The McLarens were cooler than every other team. I'm aware of them using the thermal cameras this weekend but though it was monitoring the tyres themselves not the cake tin.


If that is true than its suggesting something is going on there. And seems he is talking from an area of expertise in phase changing materials.

I thought that using phase-changing material for brake cooling would be illegal under the current F1 regulations.

If a PCM changes state (like from solid to liquid) and affects either the brake duct airflow, mass distribution, or cooling rates dynamically, it could be classified as an illegal moveable aerodynamic device or thermal control system.

[AR3-GP]

What is a bimetallic strip? If you mend together two pieces of metal with different thermal expansion coefficients, the resulting bi-metal strip will tend to curl towards the side of metal with the higher expansion coefficient. Why do most metals expand when heated? Anharmonic potential wells. Can a material shrink when heated? Yes, that can happen too, but not that common. Anyway, such a scheme could be used to open and close a passage within an air duct.





In this way, you could use brake disc heat to move a bi-metal strip inside the brake ducts.

[DiogoBrand]

A few points to consider:
1. In my interpretation a bimetallic strip would be considered a movable aerodynamic device and, therefore illegal, so I don't think that is it;

2. Is it actually possible that the brake ducts would have a significant impact in drag? I mean, in terms of frontal area, brake ducts are pretty much the same for every team. Also, brake ducts take air through a complex path for every car, regardless if they're the most advanced on the field or not, so it really doesn't make sense to me to think that a significant part of the straight line disadvantage of McLaren comes from these ducts;

3. Last year there was already discussion of a magic solution from McLaren to improve tire cooling, the infamous "water on the tires" idea from Red Bull, and by that point there was no evidence of anything different on their brake ducts, so can we tell for sure if the brake ducts are the main factor for this advantage?;

I believe that focusing so much on one aspect of the car is a bit misleading. They went from one of the worst cars on the field to one best in Miami last year, changing front and rear suspension and brake ducts, front wing, sidepods and engine cover. This year they have a different front suspension layout, with a more aggressive anti-dive geometry that some people even questioned if they could make work, they have a different sidepod inlet to everyone else, different cooling outlets and we don't even know what their floor (or anyone else's) is doing. One of their biggest advantages at Miami was in low speed, which suggests good mechanical grip, which could also be related to a suspension that's gentler on tires. So to think that most of their advantage comes from brake ducts is in my opinion an oversimplification.

On a lighter note, I know it must have been hard for some people to see McLaren have a dominant car for 6 races after 8 years of Mercedes dominance and 3 years of Verstappen dominance, but I believe it's all over now that Zak drank all the tire water so no worries anymore.

[AR3-GP]

Is the silver brake duct material thermally insulating or thermally conducting? I think it's not a coincidence that it appears on multiple cars.

[AR3-GP]

Front brake ducts




https://it.motorsport.com/f1/news/f1-mc ... /10704690/

[Watto]

A few points to consider:
1. In my interpretation a bimetallic strip would be considered a movable aerodynamic device and, therefore illegal, so I don't think that is it;

2. Is it actually possible that the brake ducts would have a significant impact in drag? I mean, in terms of frontal area, brake ducts are pretty much the same for every team. Also, brake ducts take air through a complex path for every car, regardless if they're the most advanced on the field or not, so it really doesn't make sense to me to think that a significant part of the straight line disadvantage of McLaren comes from these ducts;

3. Last year there was already discussion of a magic solution from McLaren to improve tire cooling, the infamous "water on the tires" idea from Red Bull, and by that point there was no evidence of anything different on their brake ducts, so can we tell for sure if the brake ducts are the main factor for this advantage?;

I believe that focusing so much on one aspect of the car is a bit misleading. They went from one of the worst cars on the field to one best in Miami last year, changing front and rear suspension and brake ducts, front wing, sidepods and engine cover. This year they have a different front suspension layout, with a more aggressive anti-dive geometry that some people even questioned if they could make work, they have a different sidepod inlet to everyone else, different cooling outlets and we don't even know what their floor (or anyone else's) is doing. One of their biggest advantages at Miami was in low speed, which suggests good mechanical grip, which could also be related to a suspension that's gentler on tires. So to think that most of their advantage comes from brake ducts is in my opinion an oversimplification.

On a lighter note, I know it must have been hard for some people to see McLaren have a dominant car for 6 races after 8 years of Mercedes dominance and 3 years of Verstappen dominance, but I believe it's all over now that Zak drank all the tire water so no worries anymore.
https://preview.redd.it/zak-browns-wate ... 25dcbb955a

I am skeptical too if they would be movable aero devices but I did see someone speculate there maybe a loophole that essentially they may not be really aero, from Fitting Mechanics here

That side probably start to come under movable aero device I would imagine - similar to the blown wheel nuts Mercedes had a few years ago that were eventually banned for being movable aero, I guess depends how much they can keep this quite from the FIA. describe it well enough without going into full detail. But if discovered would I think almost certainly come under protest.

Not sure if there is a loophole around that, but let's imagine that the bimetallic strip is not exposed to the air stream, it is fully enclosed and only serves to improve or reduce conductivity of heat toward the rim. So if the rim is too cold, it "connects" to the hot brakes and conducts heat, if it is colder it disconnects. All fully enclosed and air sealed. This wouldn't be moveable aero.

But it wouldn't fit the theory that McLaren has more drag because of it, if that is accurate.

I think what points to the brake ducts having something to do with it though was RBR use of thermal cameras on the brake drums showing the McLarens cooler than every other team during pit stops.so I doubt that anything to do with suspension engine covers etc as I think (no expert) that is unlikely to effect the brake temps. tyres sure but brake drums temps suggest something else.

Was pointed out too the McLarens seem to be able this year to bring tyres upto temp very quickly and keep them there/

There is more to it than just that no doubt they seem to get good drive out or corner and traction zones (but could be lightly related to the above is tyres stay in an optimum range.

They are still I think the best are riding the kerb so that wouldn't be anything to do with the brake drums to me.

[AR3-GP]

Teams make use of double baskets to try to isolate the tyres from the heat source of the brakes.

A first carbon cover goes around the brake calliper and disc, which has specific ducts that extract the hot air towards an outlet that exits behind the brake ducts.

The second basket acts as a buffer, with a cavity created between the wheel and the first drum where fresh air can be channelled to help cool things down.

https://www.autosport.com/f1/news/mclar ... /10635736/

[ispano6]

Teams make use of double baskets to try to isolate the tyres from the heat source of the brakes.

A first carbon cover goes around the brake calliper and disc, which has specific ducts that extract the hot air towards an outlet that exits behind the brake ducts.

The second basket acts as a buffer, with a cavity created between the wheel and the first drum where fresh air can be channelled to help cool things down.

https://www.autosport.com/f1/news/mclar ... /10635736/

Reminds of a Dewar flask or thermos, but there is no vacuum I assume. I think it is what Stella says it is, a clever solution and not necessarily super high tech but still innovative.

[AR3-GP]

Teams make use of double baskets to try to isolate the tyres from the heat source of the brakes.

A first carbon cover goes around the brake calliper and disc, which has specific ducts that extract the hot air towards an outlet that exits behind the brake ducts.

The second basket acts as a buffer, with a cavity created between the wheel and the first drum where fresh air can be channelled to help cool things down.

https://www.autosport.com/f1/news/mclar ... /10635736/

Reminds of a Dewar flask or thermos, but there is no vacuum I assume. I think it is what Stella says it is, a clever solution and not necessarily super high tech but still innovative.

The flask comparison is interesting. If you could generate a vacuum (or at least some very low pressure) in one of the shells, then there could be an insulating effect. We don't know the magnitude of the thermal inputs and outputs so it's hard to say if that is what you need here. From what is reported, the teams move air through the "shell" in order to cool the rim, but I can't judge whether vacuum-like insulation barrier would be more effect. If it were, then brake disc could be used to pump the air out.

[ispano6]

The flask comparison is interesting. If you could generate a vacuum (or at least some very low pressure) in one of the shells, then there could be an insulating effect. We don't know the magnitude of the thermal inputs and outputs so it's hard to say if that is what you need here. From what is reported, the teams move air through the "shell" in order to cool the rim, but I can't judge whether vacuum-like insulation barrier would be more effect. If it were, then brake disc could be used to pump the air out.

In Japan the use of thermo's to take hot food to school or work is common. A trick to keeping food hot until lunch time is to first fill the thermos with boiling water and leaving it in for around 5 minutes, then dumping it and placing your heated food and closing it shut immediately afterwards. My kid has never complained about cold lunches since. It's called a "magic bottle" in Japan and I take it to work and fill it up with frozen yogurt available in our office and bring it home to the kids and it's perfectly cold as needed.

I imagine you could do the same and fill it with ice water or dry ice and sealing right afterwards and the thermos would retain the chilled state for several hours. I wonder if the water in the tyres that Horner has alluded to is actually a coolant that is used to chill the drums and leave it chilled for as long as needed during the race and dissipates toward the end. Maybe Zack was being cheeky with the tire water stickers on his thermos

[FittingMechanics]

In Japan the use of thermo's to take hot food to school or work is common. A trick to keeping food hot until lunch time is to first fill the thermos with boiling water and leaving it in for around 5 minutes, then dumping it and placing your heated food and closing it shut immediately afterwards. My kid has never complained about cold lunches since. It's called a "magic bottle" in Japan and I take it to work and fill it up with frozen yogurt available in our office and bring it home to the kids and it's perfectly cold as needed.

I imagine you could do the same and fill it with ice water or dry ice and sealing right afterwards and the thermos would retain the chilled state for several hours. I wonder if the water in the tyres that Horner has alluded to is actually a coolant that is used to chill the drums and leave it chilled for as long as needed during the race and dissipates toward the end. Maybe Zack was being cheeky with the tire water stickers on his thermos

But having supercooled isolated wheel drums would make McLaren car have issues with tire warmup. This doesn't seem to be the case. What you outlined would more fit with the cars that used to have good race pace (tire deg) but couldn't qualify well.

The way McLaren behaves almost looks like they have some kind of variable cooling, depending on needs. Maybe it is just a cooling system that is very suboptimal when at lower speeds (like in safety car laps or outlaps for quali) which allows them to build up temperature in the drums. This would allow them quick warmup but then when they are doing hotlaps it would super cool the drums. Only thing that doesn't fit for me with this theory is that this should mean they can't fire up the tires after pitstop, they can't do a slow lap after a pitstop so the cooling system should be "on" immediately.

[_cerber1]

I imagine you could do the same and fill it with ice water or dry ice and sealing right afterwards and the thermos would retain the chilled state for several hours. I wonder if the water in the tyres that Horner has alluded to is actually a coolant that is used to chill the drums and leave it chilled for as long as needed during the race and dissipates toward the end. Maybe Zack was being cheeky with the tire water stickers on his thermos

Any substance other than air will have weight, which will negatively affect the unsprung masses and the overall weight of the chassis. It will also contribute to the formation of condensation, which will flow through all possible cracks. In addition, such a thing will be very difficult to hide.

[DiogoBrand]

We are assuming that McLaren is somehow using brake heat to heat up the tires, then once they're up to temperature they're isolating them to prevent overheating, but is there any evidence that they're doing something special to bring the tires up to temperature?
I mean, maybe heating up the tires is not such a challenge, and the brake ducts are only acting to isolate brake heat from the tires, not switching on and off to do two different functions at different times. They do have an advantage in keeping the tires cool over a qualifying lap when temperatures are high, but I don't see them having a big advantage in qualifying or race pace otherwise.