Low downforce and a smooth, gripless surface make Mexico uniquely cruel to tyres
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Intrigue around Mexico City’s altitude effects on the cars this weekend is particularly intense ahead of the event.
You probably know how the thin air at such an altitude reduces downforce so much that you end up running Monaco levels of wing but achieving Monza levels of speed. It’s a cliché but it’s true.
It also brings immense challenges in cooling the brakes (fast straightline because of reduced air resistance, but low corner speed because of reduced downforce plus the fact that the cooling air is 25% less effective at cooling than at sea level).
But the particular ’26 intrigue concerns cooling of the new power units and the effect of the reduced downforce upon the ’26 generation of tyre. There’s room for all sorts of competitive upset there.
Last year’s McLaren had a big cooling advantage over everyone. In both brake cooling and PU it enjoyed a technological advantage which exaggerated its superiority whenever cooling demands were extreme. Part of the ’26 regulation change took away the technical advantage of their brake cooling and therefore their rear tyre temperature management.
Furthermore, the PU cooling advantage – which was such in ’25 that the bodywork needed far fewer airflow-damaging cooling outlets in high temperatures than the others – also seems to have gone. The last time this year we had a very high cooling demand was in Budapest and although the car was dominant there, it didn’t have noticeably fewer bodywork openings than the competition.
Mexico’s thin air makes cooling a compromise; McLaren shone in that area last year
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The cooling demands of this year’s more powerful batteries are far higher and it remains to be seen how the power units compare on that, as well as the usual differences in this altitude’s impact upon the various turbo size choices made by everyone. In this altitude, it can be that a bigger turbo cannot reach its boost targets as easily as a smaller, faster-spinning turbo. There are cooling implications around that too.
But the biggest potential for competitive variability imposed by the altitude is perhaps tyre behaviour. The low downforce and smooth, gripless surface makes Mexico City the most difficult track of the year in which to match the temperature of the tyre’s tread and its core. For a given ambient temperature the track surface is invariably super-hot because the thinner altitude filters out less radiation, as there are fewer air molecules to scatter or absorb it. This in combination with the tyre’s excessive sliding on the gripless surface/low downforce (because of the thin air), means it’s very easy to quickly overheat the tread of the tyre.
So quickly, in fact, that the core can still be under-temperature and therefore brittle and inflexible, even as the tread is wildly overheating. The quick warm-up can help you on a qualifying lap but if it’s too quick it will cripple you over a race stint through missing the window to get some load into the core before the tread overheats. The internal core temperature of a tyre typically takes five-six laps to stabilise.
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Obviously, you won’t achieve that for a qualifying lap as there isn’t enough time. Instead, you derive the grip from the fresh surface of the tyre and you’re essentially abusing it because the core is still quite rigid and so not bending much – lending the surface less help. The elasticity of the core as it bends to oppose the force gives the tread less work to do. But it doesn’t become fully elastic until it’s been warmed by the loads being fed into it over a period of laps.
On a smooth surface with not much downforce, the loads fed into the tyre are relatively low frequency. So the core isn’t getting much help. A slowly heating core and a fast-heating surface means there’s only a limited amount of time to get the tread to feed in adequate loads to the core to bring it up to temperature – after which the tread is too hot to do that. The smoother the surface, the smaller that window and if you miss the window, that’s it.
The ’26 cars with less downforce will, in theory, be even more susceptible to this, although the smaller ’26 tyres may alleviate that. But the distinction between a fast qualifying car and a fast race car will probably be sharper here than anywhere else we’ve been this year.
Let’s see how it pans out.
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