An intriguing theory as to where McLaren’s advantage over the field may stem from has been put forward by a motorsport engineer.

With McLaren’s MCL39 enjoying an advantage in tyre life that has rival teams scratching their heads, a prominent motorsport engineer has put forward a theory.

McLaren braking theory put forward by motorsport engineer

McLaren’s advantage appears to be particularly prevalent over a race distance, with the MCL39 matched by Red Bull’s RB21 over a single lap – as Max Verstappen has already proven on several occasions in qualifying this season.

In Miami, at a circuit with high track temperatures and high tyre wear, McLaren’s advantage proved huge over a race distance as Oscar Piastri and Lando Norris came home over 30 seconds clear of their nearest rival.

What has become clear and known to the other teams is that McLaren’s advantage seems to stem from its ability to keep its tyres alive by keeping their temperature lower than what the other cars can manage.

As temperatures climb and others start to struggle, McLaren can continue at unabated speed – an advantage that increases, rather than shrinks, as a race plays out.

But an understanding of how McLaren is doing it has not yet been figured out although rival teams, like Red Bull, have been reported as using thermal cameras to spot how McLaren’s brake drums are consistently cooler than theirs – information which has been shared with the FIA.

The FIA took a very close look at the rear brake design of the MCL39 after Miami, using its usual post-race checks of a single car to select a McLaren and forensically examine an area of interest.

With the indications being that the design has been found legal, the FIA will confirm its findings on Wednesday this week but, assuming legality, no further details will be disseminated by the governing body.

But what is becoming more clear is that some very clever engineering has gone into the McLaren’s rear brakes, and, more specifically, the brake drums and cooling – the heat from the braking system transfers into the tyres so, the cooler the brakes are kept, the less heat is transferred into the tyres.

While the parameters pertaining to brake drum dimensions and the design itself is controlled under the technical regulations, what is less controlled is how they are cooled, ie. the internal airflow ducting, as well as the materials used in the cooling configuration.

A motorsports engineer, Martin Buchan, who boasts a background with Audi and Force India/Racing Point before establishing his own motorsports consultancy company, also worked with McLaren Advanced Technologies, with whom he carried out research on the use of ‘phase change materials’.

It was during his time with McLaren that Buchan wrote his doctoral thesis on innovative cooling technologies, which happened to be on the use of such materials for use with cooling high-voltage batteries as used in Formula E, with the research having crossover into other areas of cooling.

F1 teams face a difficult balancing act with their brakes, requiring the cooling systems to keep the brakes at an optimal temperature to provide maximum bite but without overheating, whilst also ensuring the heat doesn’t transfer excessively to the rims and overheat the tyres.

Towards the end of last season, McLaren found itself at the centre of allegations that it was using water in its tyres to cool them – a scenario which CEO Zak Brown poked fun at in Miami by showing up with a water bottle marked ‘Tire water’ on the pit wall.

While no evidence of such a practice was found by Pirelli, Buchan’s theory does hypothesise that the phase-changing material does bring liquids into the scenario.

His theory is that the use of phase-change materials in a shielded channel between the brake linings and the inner working of the brakes transfers from solid to liquid when a certain temperature is reached, but the temperature does not climb any higher as a result of it changing from a solid.

The material used would determine the point at which the temperature stops rising, with the temperature of the brake drum triggering the phase change – perhaps explaining why the advantage is not as marked in qualifying as it is over a longer distance.

Then once the brakes cool down again, the material re-solidifies by the time the car is back in parc fermé.

How likely is this hypothesis?

Paddock sources have indicated to PlanetF1.com that such a hypothesis does have some merit, with McLaren clearly “stronger in this area” than every other team.

It’s been quite a while since F1 has had an innovative breakthrough made by a singular team, with Mercedes’ DAS system perhaps the last example of true ingenuity in an era of highly prescribed technical regulations.

What is known is that the use of such materials would go some way to explaining why ‘water in the tyres’ was put forward as a hypothesis late last season. It’s also worth remembering that McLaren came under scrutiny ahead of last year’s Hungarian Grand Prix, having raced with holes left uncovered from temperature sensors in the rear brake drums – holes that are only permitted to be left uncovered after practice.

The FIA was in touch with McLaren to quietly remind the team to cover up the holes, with the assumption having been that it was an operational oversight – a scenario which may appear very different in retrospect if the team was in the early stages of its development of the use of such materials.

If the use of phase-changing materials does prove to be the big differentiator, it’s logical that other teams will seek to copy the same idea.

Is Red Bull currently carrying out similar experimentation? After all, Verstappen has recently encountered unusual braking issues during races – including Miami – for which proper explanations have not been forthcoming.

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